1. The Practical Aquaponics discussion forum has been in operation for the last 5 years...

    We have enjoyed giving this service free of charge however ongoing increasing financial costs of running this service is making it increasingly difficult. Up until now we have resisted advertising as a means of a revenue stream to help run this forum but it has become inevitable that extra revenue is required to run this forum.

    We have introduced a donate button to help offset the cost of running this forum. It is completely voluntary, but if you would like to donate, all donations would be greatly appreciated.

    Thanks Murray..
    Dismiss Notice

Balcony kit at Hillview (Qld)

Discussion in 'New Aquaponics systems - off-the-shelf ready to go' started by miadeb, Mar 26, 2010.

  1. Yabbies4me

    Yabbies4me Administrator Staff Member

    Joined:
    Jul 27, 2010
    Messages:
    5,788
    Country:
    Australia
    State:
    W.A.
    City:
    Perth
    Hi Miadeb,

    What does being a moderator have to do with?... moderators are allowed opinions just the same as any other forum member... Why does it have to be about what you think?

    Are you saying that if it had been anyone other than a moderator disagreeing with you it would have been acceptable?

    At the time you and Rupe were having this discussion, he was not a moderator, hadn't been for quite some time.

    By all means discuss the balcony kit etc, but the side issue you and Rupe were discussing... I wouldn't bother carrying the conversation forward and wasting your time responding to Rupe's previous replies... it's a moot point now!

    Cheers,

    Yabbies.
     
    Last edited: Sep 21, 2012
  2. miadeb

    miadeb Member

    Joined:
    Jan 23, 2010
    Messages:
    81
    Country:
    Australia
    State:
    Qld
    City:
    Hillview
    Potassium nitrate injection.

    I have been adding potassium nitrate for some months at a rate of about 5 grams twice weekly. The results have convinced me to take it up as a regular part of my warm weather program.


    I had 4 cucumber seedlings last spring, spaced along a grow bed that was partly flooded from the inlet end. All the seedlings were stunted after some weeks, more so at the flooded end and the most flooded had died at the time I started nitrate injections. Growth in the cucumbers was then vigorous and we harvested cucumbers every two or three days. This is worth repeating except that eventually the grow bed was totally clogged. By then the cucumbers were covered in white mould and dying so cleaning them out was no loss.


    In previous years, in the warmer seasons buffering here was always with lime to keep pH up. This last summer was different. Over two extended periods buffereing was with dilute hydrochloric acid to hold pH down. The only difference this season from the previous was the nitrate injection. Argue that it is not the nitrate uptake that pushed the pH up if you want, as has been done above, but I see what I see and go with it. I will repeat the program next year with an expectation that I will see the same result.


    Twice I harvested by cutting plants away to leave their roots behind to rot in place. I believe this rotting is associated with the generation of organic acids and that this pushes the pH down. Normally I would grow plants with small, compact root balls that can be pulled up to leave a minimum of vegetable material behind. This makes it easier to keep pH at a target level. It reduces clogging. With roots in place, for a period afterwards, system pH fell to need a lime buffer along with the nitrate injection. So what I have seen this season is consistent with the idea that deep dives in pH are caused by the rotting plant material.


    Now the picture for me is as follows. Fish add ammonia to water. Ammonia in water is a weak base. The bacteria process the ammonia though nitrite to nitrate and the water is then acidic. Plants take up nitrate and this can leave the system neutral. Add extra nitrate and the pH can go up. Leave roots behind to rot and the pH can go down.


    Note that if nitrate uptake takes pH up, nitrate is not an effective buffer against diving pH except around pH 7 as the further the system is driven from that point the more buffer is needed to move the ph by a set increment. You cannot keep adding nitrate beyond what the plants can take up. At my injection rate of 5 grams twice weekly there was nothing to show on the API nitrate test except recently as temperatures dropped. This is consistent with the story that nitrate uptake is affected by temperature.

    Dennis
     
  3. miadeb

    miadeb Member

    Joined:
    Jan 23, 2010
    Messages:
    81
    Country:
    Australia
    State:
    Qld
    City:
    Hillview
    To clean a growbed, or not.

    At what point is it finally necessary to proceed to washing growbed media? Our beds have operated with clay balls for three and a half years with no cleaning done yet. Whilst it might be useful to clean now, I do not see that it is absolutely necessary. There appears to be some mechanism at work by which a clogged bed will recover, something temperature dependent as it works best in warmer times.


    I am inclined to let things run to a point of failure at least once, as you will see below, so as to know what things must be done. How can you prioritise if end results are not known?


    I reported in the last post some success with cucumber and its demise. What finally triggered action to remove it was its growbed being completely clogged. I monitor how open the beds are by counting down how quickly the siphon discharge is completed (both fill and drain times relate to free space, but drain is faster and quicker to count down). I take times over 20 secs as good (depends on grow bed size). Below ten is restricted. The siphon triggers sooner as the bed clogs as there is little of the bed remaining to fill and at the cucumber kill it had gone down to nothing with a constant trickle discharge. I cleared away everything by cutting the vines off at the surface to leave roots in place. The bed was left fallow and after a week or two the siphon kicked in and the bed began to clear. Soon it was back to an acceptable level of operation. The roots, left in place to rot, triggered acid production and reversion to liming after a period running the other way with use of an acid buffer.


    This is not the first time I have seen beds recover a more open state. There is clearly some mechanism at work for this. This year I have only fed commercial fish feed pellets. I have not added any plant material as food. This way there was only fish waste and roots to clog the beds. We have compost worms to feed on rotting roots but I expect there will be other agents. I have put samples under a microscope and seen small, 2mm, white coloured worms and some flea like entities. Pulling a plant out with its roots releases a cloud of detritus into the fish tank and its return to the grow bed sees it settling at ponded inlets. This material is vegetable matter. Dig into the bed for a sample and there is both the vegetable matter seen at the ponded inlet and other less distinct material. Does all this material clear away over time? Or, if there be a build up of permanent deposits, for how long can it be ignored? And what constitutes any permanent deposits? Does it cause any adverse actions?


    The fish in our system are three and a half years old, the same age as the grow beds. None have died in recent times. We have not salted, used a hospital tank, or added potassium permanganate. The water is clear except at a plant harvest. The water has no foul odour. The fish grow and pass to the plate with no taint. This means to me that any build up in the beds is not harmful, that there is no reason to fear it. So when should it be cleaned away?


    The one indicator for a clean as I see it would be too great a loss of siphon function from clogging. Currently this is held at bay here by use of fewer plants, by use of plants whose roots are short and easily removed, together with lower fish feed rates than seems usual across the forum. The only penalty I see for a gain in avoiding cleaning is reduced output from the system. If you can live with this, how long might cleaning be deferred?

    Dennis
     
  4. Yabbies4me

    Yabbies4me Administrator Staff Member

    Joined:
    Jul 27, 2010
    Messages:
    5,788
    Country:
    Australia
    State:
    W.A.
    City:
    Perth
    ...
    At some point in the future your beds may become so full of rotting waste that anaerobic areas form, which will increase the alkalinity of the system, so your system pH will cease declining, stabilise for a while, then start to rise.

    When it gets to the point, after years of the pH continuously dropping and you having to add Calcium Hydroxide or Potassium bicarbonate to control it, that your pH stabilises and/or begins to rise, then I would suggest it’s time for a GB clean out.

    I haven’t experienced this yet with my systems, but I have a number of customers that have and the time frame varies. I’ve heard time frames from customers and other forum members from 2-5 years... I think it was Murray that said one of his beds even took 6 years.

    ...or, it's also probably time to give the beds a clean out when everything is clogged to the point where it affects the reliability of the system... as you are now experiencing.
     
  5. Murray

    Murray Site Admin Staff Member

    Joined:
    Jun 4, 2009
    Messages:
    7,609
    Country:
    Australia
    State:
    Queensland
    City:
    Brisbane
    Just a word of advice on bed cleaning. Make sure you clean the bed by whatever method you choose but do not let any of the dirty water run into the system. OK you have hosed the pebbled down or replaced the gravel and there is still a fair bit of residual stuff/muck there. It would appear to be ok to just let the grow beds clean up the water afterwards, but this dirty water, even though it is not all that dirty can cause problems. There is most likely a concentration of anaerobic bacteria in that residual material that was "locked up" when the bed was still intact, but by allowing this old material to freely circulate in the system, even if only for a few days while the system picks it up again, can put oxygen stress and bacterial stress into the fish.

    The bacteria "Columnaris - Flexibacter columnaris" is more than likely present in the system and is kept in check by the system being in balance. Amajor disturbance of the system by a poorly executed grow bed clean out, may give the bacteria a chance to rapidly multiply and cause trouble for your fish.
    If the fish slime coat is disturbed at this time by a rapid increase of suspended solids, coupled with a dramatic drop in available dissolved oxygen, then the fish are very open to infection taking hold.
     
  6. miadeb

    miadeb Member

    Joined:
    Jan 23, 2010
    Messages:
    81
    Country:
    Australia
    State:
    Qld
    City:
    Hillview
    Growbed dry patch

    A development after the cucumber clogging described in my last post, this time in a melon bed, a development that was new to this system, was a patch of bed midway between inlet and outlet that was dry. Put a trowel in and the clay balls came up barely damp and gummed together with a grey/black goo. Water was not going through this section. Flood and drain was operative so the flow from inlet to outlet had to be under this blocked centre section. The bed was channeled. The melons were cleared away and this section was left alone. The patch of dry bed diminished in size over time. Now a trowel sunk into this area to turn up the media brings up balls that are both wet and clean. Once again there is a recovery mechanism at work.


    People on the forum have described AP as an ecosystem. This implies it is capable of existing independently, that there are processes that bring the system back into balance if it be perturbed. I was initially sceptical of these claims and did consider a rebutal. I held off. Good thing. I now have experimental results, real world facts out of our system, to support the view of AP as an ecosystem (forgetting the fish food inputs). I have to concede the claim may have some validity. But to what degree? There is a decomposition process but can it be utilised? It may have adverse consequences at some point.


    Y4M names a risk. What I seek in my leaving things be is to see if this risk can be quantified. It is one thing to be told there is risk but another to know its probability. Quantification of risk is the key to prioritising and establishing efficient management practices. The shortest cleaning cycle I have seen mentioned is every 6 months. I doubt many are working this regime. Buildup of material to be cleaned will vary with feed rates and plant densities. There are tests for water chemistry. What signals time to clean? Is there a sweet spot; a stocking rate, together with plant selection and management regime that will see the last fish on a plate before a clean and restocking.


    The only input to our system is fish food (the nitrate injection being an exception over the last warm season). Fish waste collected in the growbed is the only source of nutrient to our plants. If we clean the bed this nutrient bank is lost. Clean often and plant production is reduced. That can be rebuilt by adding nutrients. But, can you say you have an ecosystem if you follow the lead on other threads and put in nutrients from decomposition processes done outside the system (seaweed extract etc)?
     
  7. Murray

    Murray Site Admin Staff Member

    Joined:
    Jun 4, 2009
    Messages:
    7,609
    Country:
    Australia
    State:
    Queensland
    City:
    Brisbane
    Good point, so, whenever we have cleaned beds we only do one at a time, and if possible a month or two apart for this very reason.
     
  8. miadeb

    miadeb Member

    Joined:
    Jan 23, 2010
    Messages:
    81
    Country:
    Australia
    State:
    Qld
    City:
    Hillview
    Stocking rate

    I like the staggered cleaning plan Murray. We have had one bed empty for some weeks to see what clearing might occur in the current colder weather. Not much has happened. The ponding and discharge time seem fixed. May proceed with a clean soon.


    Three and a half years after stocking with 100 silver perch fingerlings we have about 15 fish remaining. The biggest taken out this year weighed in at 560 gms. However there are two that would not reach 50 gms, and most of the remaining fish are likely to weigh in between 100 and 200 gms. There are two that will be close to 400 gms, our only fish meal in the near future.


    We ate all our larger fish early, coming out of last winter, to reduce fish numbers to the smallest twenty, the plan being to see if the smaller fish would grow to a decent size when the larger were not taking the bulk of what food the system could handle. Results are not promising.


    Some on the forum hold there are consequences to a 100 fingerlings per cubic metre stocking rate.


    One argument is that there is a welfare issue. Is this a real concern? And if so what number is not? The NSW DPI reports on much work done with silver perch and abstracts of research papers can be found on the net. One trial looked at the fish in ponds, but restrained in 1 cubic metre cages, using stocking rates of 12, 25, 50, 100, and 200 per cage. Interestingly, the 25 and 50 fish exhibited aggression and there were losses. Better growth was found in the higher number cages. Note, these are cages in ponds, not an isolated one cubic metre body of water. But still they are confined. Is there a welfare issue? If there are problems with lower stocking rates why not go higher?

    Another argument is that overstocked fish would grow at different rates. There is a reference in the forum describing the disparate sizes as 'runts' and 'bolters'. Are the 'runts' suffering? Are they permanently stunted or are they waiting? I had hoped to know something of this in the last growing season. But having knocked the population down to mainly 'runts', to give the 'runts' more access to food, we have not seen them grow significantly.


    I once saw an argument that it was natural in Australian waterways for there to be differences in sizes of various lifeforms, as the state of the waterways was unpredictable. It was good for some to be at breeding size to take advantage of the next rains, and it was good if some remained small in case the waterways dried out to ponds. It was said that a difference in size was good for survival of the species. The point is that a difference in size is not necessarily a welfare issue. Size difference can be a result of different growth rates. Given enough time our 'runts' may grow. We will give them one more season to show if their 'runtiness' is not permanent. No growth with no competition for resources should decide the issue.


    If the 'runts' grow out to a decent size fish, then which stocking rate will have the best outcome, 25 or a 100. Raising 25 and starting again three more times at 25 might take longer to see all the fish reach a set weight than starting at 100 and seeing the 'runts' idling away for a while. The last 25 fish of a 100 start might get to table weight faster than a fourth, fresh batch of 25 fingerlings.


    There are two approaches. Stock lightly or feed lightly. Both transfer fish to plate. Which does it more efficiently? Which does it more cheaply?

    Dennis
     
  9. miadeb

    miadeb Member

    Joined:
    Jan 23, 2010
    Messages:
    81
    Country:
    Australia
    State:
    Qld
    City:
    Hillview
    Zones in a clay ball bed.

    I like AP for its food, food for both nutrition and thought. What follows are observations in a clay ball system in cold conditions. Skip it if you dont like analysis.


    I was watching a growbed with no plants, waiting to see how decomposition processes might operate in this warmer winter. Not much was happening. The drain time was fixed at 25secs. I wondered what this represented as full flood and drain free space. I put a measuring jug under the bed return to the tank and counted off seconds to fill and using the drain time and drain rate revealed by measurement, the discharge volume was about 12 litres. This is the full flood and drain volume in an old bed (with settling and accumulated waste). Quite small. Not surprising that higher feed rates and/or more dense planting overwhelms the system.


    Our beds have been operating with a section in full flood and drain mode around the siphon and a permanently flooded section at the bed inlet, a section that I expect still flows as plants grow there to indicate some level of oxygenation, only not as freely as to permit ebbing with the siphon action. In addition to these two sections I expect a layer across the bottom, below the siphon break point, that is without any influence of flow through the system to be anaerobic, a sort of sump. It may be higher away from the siphon as waste slows flow. A question I ask myself is where is decomposition most effectively taking place? Should I be bothered by the extent of any of these three sections? I expect they are there in all older grow beds using clay balls, to varying degrees. Cleaning will eliminate the permantly flooded section for a time but I expect this is the more important one for decomposition as a source of nutrients for plants when a system is run with fish food as the only input. What might be the best ratio of full flood and drain to permanently flooded sections? With 12 litres in the flood and drain section how much is in the permanently flooded section? There are a number of ways by which to arrive at an answer.


    With a bed cleared of plants a drop in the height of the media after 3.5 years was obvious. Some 2cm down. The bed had settled over time. The media was more closely packed. If you do not know what this means take some coins and array them first on a square grid, four coins touching, and again on a triangular grid with three coins touching. Look at the gap between the coins. The hole between four coins is larger than with three. Tumble clay balls into a grow bed and there will be some caught with a larger pore size between them that is lost as they settle over time to their closer packed configuration. Some of the free space that existed in the beginning, the working volume of the growbed, is now filled out with balls and lost. How much? Is it significant?


    For the media level to be lower some of the media free space that allows the flood and drain action had to have been taken up by sunken clay balls. I tumbled clay balls into a bucket, topped it up with water, poured off the water and measured its volume. The result was that 2/5 of the total volume was free space, leaving the balls occupying 3/5. In our grow beds the flood and drain volume, the working volume, extends from the siphon break point up to the top of the stand pipe and it is half the bed depth when freshly loaded. If 2cm have sunk then half of that, 1cm worth is taking out the working volume. Work out the bed volume in a 1cm layer and subtract 3/5 of that from the loose packed working volume to know what the reduced working volume is in a settled bed. The loose packed working space, freshly loaded, is about 34 litres in our system and 30 litres when close packed. Not much of a difference, but pore size will be down and that could be significant. These figures do not take acount of roots and fish waste. The drain rate based measurement above has the working volume reduced to 12 litres so there is 18 litres taken off full flood and drain by retained waste.


    Working another way, with 34 litres free space the drain time would then be 68 secs if the drain rate is the same as for the close packed bed. What is the actual drain time in a loose packed bed? Cannot remember how it was 3.5 years ago.


    I cleaned the plant free grow bed out of curiosity. Where the bed drained in 25 secs before cleaning, it drained in more than double that afterwards as you would expect with a bed now more open by both less close packed and being freed of waste. Whilst it was over 60 secs initially the drain time quickly reduced to around 50 secs. Time the filling of a measuring jug under the tank return from the growbed to reveal the clean bed drain rate. Where it was 2 secs per litre in the close packed bed before cleaning, after cleaning the drain rate was 1.5 sec per litre and at a drain time of 50 secs in the cleaned bed, 33 litres of working space was indicated. This compares favourably with the cleaned working volume of 34 above by the volume method so I think the figures are right, nothing significant has been overlooked. The conclusion is that in our old beds, worked harder this last growing season, 2/3 of working space was occupied by roots and fish waste leaving 12 litres for flood and drain action when drain time was 25 secs. The drain time dropped away with further pressure as described in an earlier post. As I said above I expect some flow through the clogged sections as some plants will grow in clogged areas, but a flow too slow to ebb with siphoning. Which ratio of these two volumes will deliver the best result in warmer weather when decomposition takes place? With little decomposition in the cold, with plant growth continuing along with a little fish feeding, the build up should increase as it did in previous winters. Clearing is a summer process.


    I saw nothing in the cleaning that suggested to me that cleaning was essential at that point. There was nothing there that was not there a year ago. There was fish waste evident at the inlet end and some partially decayed plant roots remaining throughout the bed, left after harvesting earlier with roots left behind. What was there could be expected to decompose as had other blocks of waste in the past when the environment heated up. What cleaning has achieved is restoration of a waste free, loose packed working volume. What cleaning has done is to increase pore size. Pore size could be made bigger by using larger particles. The process I used for cleaning did not isolate what was in the bottom, the sump section (I filled the bed with water to ease removal of the clay balls and everything became mixed). Will have to work on another bed to know what is down there.


    For those who have not seen the clay balls, their size is typically between 5 and 10 mm, with some balls outside this range both smaller and larger. The pore size is less than with 20 mm drainage gravel. Which pore size will be best; that of the 20mm gravel, the loose packed clay balls (constant cleaning) or the clay balls in the settled, close packed configuration? Pore size will affect local flow rates, and the environment for decomposition processes.


    In addition to compost worms, I have observed other life forms in our old beds in which pore space is now limited. Are these aiding decomposition? What might exist in a more open one? If a larger population is accomodated in a more open media will waste be disposed of more quickly? It is apparent from other's threads that some are putting more fish waste and plants through their systems than we do, and 20 mm gravel is common. Is size the key or are all the higher pressed systems operating with prefilters. It may be that our choice of clay balls limits our system's performance. I think the next bed that is cleaned here should be refilled with drainage gravel to see if anything stands out.


    Dennis
     
  10. miadeb

    miadeb Member

    Joined:
    Jan 23, 2010
    Messages:
    81
    Country:
    Australia
    State:
    Qld
    City:
    Hillview
    Some weeks after I cleaned a grow bed I had not seen any significant benefit. Plant growth was not impressive. Lettuce seed germinated in the cleaned bed but the seedlings were not developing until I resumed potassium nitrate injections. This was to be expected as although water temperature rose out of winter to above 20C, the fish had not resumed feeding. Little was going into the system.

    Initially I thought the cleaned bed had resulted in greater water clarity. After speaking against the need I could see myself eating humble pie. Seemed so for a while. The water was crystal clear. But as the weather warmed the water suddenly turned brown and cloudy. I have seen this before and concluded then that what caused it was caterpillars inside a mat of brahmi. Over a third of the surface area of the uncleaned beds was covered in a mat at least 5cm thick. I keep brahmi in the system going into winter in the hope it is one of the bog plants that take up ammonium directly. This action seems like a good thing to have here in winter when water temperatures can drop below that at which the bacteria might be active and conversion of ammonia to nitrate might stop. The brahmi is frost sensitive but enough survives to carry through. Assuming the problem was things living in the brahmi I started clearing the bulk of it away and the water started to clear.

    The cloudiness I put down to the presence of shredded plant material produced by slugs, snails and caterpillars becoming active as the weather warmed. I assume their dung sits on the surface and is washed in with rain. With the water clear over some weeks leading up to this event, it follows that what material was stored in the two uncleaned beds from last season must have been adequately retained there, not flowing back through to the fish tank. The problem has to be a new source of dung. This new material is fairly fine and flows freely through the system. Put a jug under the grow bed discharge, let it settle and pour off the cleared water to isolate the sediment. Under my low power microscope it looks like shredded plant material. Fish waste generated from commercial feed (no leafy greens were being added at this time) looks gelatinous with none of solid content found settling out in the jug. Whilst less of this material was flowing through the cleaned bed, the cleaned bed was not filtering all of it.

    Partially clearing the bed surface, and using a spaced planting to expose the slugs and snails to visiting birds, might reduce their numbers and help keep the system cleaner.
     
  11. Murray

    Murray Site Admin Staff Member

    Joined:
    Jun 4, 2009
    Messages:
    7,609
    Country:
    Australia
    State:
    Queensland
    City:
    Brisbane
    So true Dennis, the gravel beds don't get it all out on the first pass. It is a continuous ongoing process.
    The smaller the system the more difficult it is to have stability.
     
  12. miadeb

    miadeb Member

    Joined:
    Jan 23, 2010
    Messages:
    81
    Country:
    Australia
    State:
    Qld
    City:
    Hillview
    Yes Murray, when I see this murkiness I think it may be useful to plumb in one of the prefilters the forum describes, but then I think if I was a better gardener I would have changed plants as the weather warms to something the bugs do not like and the extra filter would not then be necessary. Interestingly all three grow beds are now taking a similar time to drain. The only cleaned bed is therefore no more free than the two that have never been cleaned.

    We are down to about ten fish. The biggest this season came out at 560gms. Some are still under 200gms and one looks to be down at 100gms. This will be their last season. I am going to close the unit down and move it onto a concrete slab. The grow beds continue to sink and the fish tank is listing. Will have an adjoining area concreted and then move the present unit onto it whilst the current location is concreted for addition of one or two more units. We want more fish. I want at least two identical units to allow comparisons to be made in order to find optimum outcomes.

    We have had a second unit (not a Balcony kit) operating on solar for about six months. This is a fast fill slow drain system with pump on timer. Currently it is on for 15mins at a time 7 times a day and only during daylight hours. I wanted to see what little overnight power would be needed so as to minimize battery size. In case nitrification bacteria might be compromised I used bog and pond plants in expectation that some could use ammonium directly. Taro, water chestnuts, and duck potato (arrowhead) are in there not because I know they work directly with ammonium but because we had them here in troughs. Taro works best. The other two are surviving but not thriving. I expect some fills at night will help and have a new timer ready for a few brief night runs. I think I can work with around 30amp/hrs a day and most of that directly off the solar modules. I expect there will be a relationship between energy in and productivity but there is also a cost. Ammonia is not a problem so something is working. I know there might be an issue with disolved oxygen with a system off at night. We have crimson spotted rainbow fish in the fish tank. The unit chosen has a surface to volume ratio similar to the still water troughs we have crimsons breeding in so I expected switching off at night should not be a problem for them. The fish have bred in the solar powered unit so I expect conditions are near enough for them.
     
  13. Murray

    Murray Site Admin Staff Member

    Joined:
    Jun 4, 2009
    Messages:
    7,609
    Country:
    Australia
    State:
    Queensland
    City:
    Brisbane
    Interesting post. Lets know how the long term results turn out on the smaller unit with the spotted rainbow fish.
     
  14. miadeb

    miadeb Member

    Joined:
    Jan 23, 2010
    Messages:
    81
    Country:
    Australia
    State:
    Qld
    City:
    Hillview
    We run two systems, similar size, same brand clay ball media, same fish feed and both on rainwater. But over the last summer and autumn the ph in one went up, the other down. All buffering in one was with acid, the other with lime. Now, in cooler weather, both are more stable. Why would one go up and the other down?

    There are differences in operation, in fish species and plants.

    The balcony kit has its pump running 24/7, flood and drain night and day. The other unit is on solar and over the period its pump was on a timer, in bursts during daylight and off at night. The bacteria in the solar unit might not be working full bore, with the system down half the day, and the effect of this would be a reduction in their driving the ph down, if, as the forum holds, the nitrification bacteria always drive ph down. This would then have ph sitting closer to neutral. It is in this system that the ph went up, requiring regular buffering with hydrochloric acid. What was driving this?

    I understand that ammonia in water is a weak base and if nothing else is at work then the ph might be a little above 7. Tests on water from the solar system indicated near to no ammonia, nitrite or nitrate but the ph climbed without regular buffering. What else is at work to drive the ph beyond that point except the plants? Both fish species (silver perch in the balcony kit, and rainbow fish in the solar unit) will be putting out ammonia and the result of this ought to be the same. Does fish dung affect ph? Do different species have a different output? I do not know but there is argument that plants do affect ph in their rhizosphere.

    Somewhere back on this thread, RoO challenged me to find a reference to support the idea that nitrate uptake might raise ph. Having done such literature searches professionally I knew the work involved and the likely limitations in any findings. I saw no point in it when a test could settle the matter. It did for me. But now this situation is different in that what was observed was happening with no additives except the buffer, hydrochloric acid. The solar system was mainly at work with taro and I thought a search restricted to this plant might turn up something definitive as regards its affect on ph. There are references to taro in hydroponics and on ammonium pushing the ph down. This is in accord with my understanding but opposite to what I was seeing and seeking to explain. It accords with the general picture that came out of the little searching I did. In this generalised picture the same plant might put the ph up or down depending on the flow of ions into the roots. If there were more positive than negative ions, or the other way around, going into the plant, then an electric field develops to oppose the flow and the plant outputs ions to neutralise it, maintaining flow and uptake of what it needs from outside. If it outputs an ion that is either acid or alkaline it affects conditions around its roots, in its rhizosphere. This is an issue in searching because none of the many inground references will be applicable in AP where the roots are constantly washed with water from the fish tank. Then the the total water volume is the plants rhizosphere and it would be sensible to wonder if the same limitations apply given the degree of dilution. What might a plant do in AP? The biochemistry across the root membranes is complex.

    Still bothered by what appeared to be an odd outcome I took an electronic ph meter around the range of rainwater filled ponds and tubs we run here. In most cases the ph was above 7 and it appeared that the more of an algal bloom in the water the higher the ph. The solar unit grows a near black algae in its tank. This is fed by the pump to the media beds to give a quite sooty look to the clay balls. The balcony kit media runs cleaner. Maybe next time I chase this issue I need to consider the algae.

    At this point I am happy with what I know and not so worried by why it is so. What I know is that the ph might go up, or it might go down. I do not need to know why it happens. In either case I respond with a buffer. Success in AP comes out of making the appropriate response to results of a few simple tests as taught on the forum, not any deep knowledge of why. Of course some knowledge of why might allay fears that the system might be out of control. Some knowledge of why might help in making improvements to processes. But in AP, at the basic level, what happens might be surprising, but what is to be done is simple, and the thing is nearly bullet proof.
     
  15. Yabbies4me

    Yabbies4me Administrator Staff Member

    Joined:
    Jul 27, 2010
    Messages:
    5,788
    Country:
    Australia
    State:
    W.A.
    City:
    Perth
    Yup!... For the average backyarder, Aquaponics is only as technical or difficult as the individual wants to make it.

    I know many AP'ers who's monitoring regime simply consists of observing the water for clarity (Ammonia makes it cloudy), looking at the fish for signs of any ailments, and checking the water pH and/or temp every week or two, or if the fish go off their feed. As well as observing the plants for any obvious nutrient deficiencies.
     
  16. Murray

    Murray Site Admin Staff Member

    Joined:
    Jun 4, 2009
    Messages:
    7,609
    Country:
    Australia
    State:
    Queensland
    City:
    Brisbane
    Excellent post Miadeb. It can be as simple or as complex as one might like to make it. +1 on Yabbies reply.
     
  17. miadeb

    miadeb Member

    Joined:
    Jan 23, 2010
    Messages:
    81
    Country:
    Australia
    State:
    Qld
    City:
    Hillview
    I operate thinking the main cause of a lack of clarity in fish tank water is the quantity of feed the system is to process. I reduce feed if the water looks off. This of course has the consequence that the fish might not be fed optimally. But they not only survive they will grow, albeit slowly as the following history illustrates.

    We are now running fishless turning out lettuces on what fish waste remains in the beds, together with potassium nitrate injections. The last 5 silvers came out with weight at 140, 160, 220, 260, and 420 grams (rounded to the nearest ten). These were 4 year old fish. Would the 140gm fish have grown more given additional time? Possibly. I think the smallest fish at the beginning of the season was about 100gms. Was it a runt or a slow grower?

    There had been little interest by the fish in food over the last summer. They became active feeders in one short period. Prior to that time there had been a thread discussing why Silvers were not feeding. I posted that it may be the weather. Someone rightly pointed out that tank temperature could be expected to be adequate at that time. And it was if a temperature over the mythical 18C was to be key. So why were the fish disinterested?

    With regard to temperature what aspect of it is thought to be key, the morning low, the afternoon high, the daily mean, the hours at a particular point, and do the fish take longer to come back when it warms up, ie, is there hysteresis. This last season the temperature was up whichever measure was considered but the fish were not enthusiastic. Growth is usually poor here, being unprotected outdoors, with water temperatures dropping in the colder months. So fish not feeding when things appear improved is disappointing.

    We had our usual dry spring and an unusually dry summer leading into autumn when we did score some good rain. But in the dry period the fish suddenly became active for a period. They rose keenly to the floating pellets and some skimmed across the surface taking multiple pellets. What bought this on? Nothing happened locally but the monsoons finally arrived and carried rain into the centre, the catchment area for the Murray Darling system, home ground for the silvers. Are the fish tuned to such events; like ants and frogs anticipating rain. Summer rains raising river levels might be a time to spawn and mature fish might feed more to build their gonads. Speculation I know but the event was real and I expect there is some explanation. Growth rates would improve markedly if the fish could be tricked into feeding at this higher rate over longer periods.

    So in our case 100 fingerlings ran out over 4 years. A small number were lost along the way; usually coming out of winter, and the last reached 140gms. Not impressive when I read here about people further south growing out trout much faster, and further north doing it with barra. Probably one fish meal for us a month. We need more units (easily done); more feed per unit (only feasible if a solids filter or extra grow beds are plumbed in); heat in winter (passive heating by enclosing the unit in a poly structure probably); or more efficient management (another balcony kit would enable some comparative testing seeking better outcomes). Will likely try all four.
     
  18. Murray

    Murray Site Admin Staff Member

    Joined:
    Jun 4, 2009
    Messages:
    7,609
    Country:
    Australia
    State:
    Queensland
    City:
    Brisbane
    Hi Miadeb,
    Your observations are spot on. Silvers can be slow growing and erratic and that is precisely why aquaculture farmers do not like them. But they are a safe easy to manage fish and tolerant of all sorts of variables. One thing we have found, introduce loads more air into the tank. We have found they feed much more when there is a load of air going into the tank.
     

Share This Page