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3 months in and a bit confused...

Discussion in 'Water Chemistry' started by Boomking, May 28, 2016.

  1. Boomking

    Boomking New Member

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    I started my system on February 15. Things were very slow until I started dosing Maxicrop with Iron. Then the growth has been out of control for the last 6 weeks or so :D. I have been dosing 80mL into my 284L system every 3rd day. I am still showing some signs of potassium deficiency mainly on the spinach. I am going to switch to K2SO4 instead as Maxicrop is way too expensive to be dosing that much. I have been getting magnesium deficiencies but my GH is 300 and my Ca is 60 (and dropping). When I see it is lacking I have been adding some magnesium sulphate about every 2 weeks or so which fixes the problem.

    I guess what I am confused about is I think GH is Ca + Mg. So my Mg should be about 240ppm and 60 ppm calcium. How can it be deficient?

    PH 7.8
    Ammonia 0
    Nitrite 0
    Nitrate 0
    GH 300
    KH 50
    P 2.5-5
    Fe 0
    Ca 60
     
  2. Yabbies4me

    Yabbies4me Administrator Staff Member

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    Hi BK,

    80ml of Maxicrop into 284L of water every 3 days is excessive and has probably led to nutrient imbalances. With our Aussie version, Seasol, the most widely recommend rate for systems already containing fish is one capful per 500L, per week.

    If you have nutrient imbalances you can have ample nutrient in the water, but they are locked out and unavailable to your plants, particularly with Calcium, Potassium, and Magnesium, too much of one and the others can be locked out.

    Are you sure the deficiency symptoms you are seeing is Potassium?... It is far more common to see Potassium locking out both Ca & Mg... Calcium deficiency can look similar to Potassium deficiency symptoms. Two reasons why I'm asking this, firstly, Maxicrop is high in Potassium and I don't know that it even contains any Ca & Mg, according to the manufacturers published typical analysis it doesn't, and you've been adding lot of it. Secondly, if your Ca & Mg readings are correct, you have far more Mg in ratio to Ca, when ideally it should be the other way around... both of these factors could be leading to a Ca lock-out.

    Also, adding both Magnesium Sulphate and Potassium Sulphate would definitely lead to sulphate toxicity in your plants in my opinion. I say this out of personal experience...

    I was adding Calcium hydroxide, Potassium bicarbonate, and Magnesium Sulphate into my system in a 3:1:1 ratio, as recommended by a friend that is a well respected hydroponic chemist. I was having to add these products 2-3 times per week because my system was stocked to it's absolute maximum safe stocking capacity and consequently there was a lot of Nitrification taking place. This ratio worked well for a period of time at keeping the Ca, K, and Mg in ratio, but after a couple of months some of my plants started showing signs of Sulphate toxicity. I stopped adding the Magnesium Sulphate for a week or so, then I resumed adding it, but at half the amount, giving a Ca:K:Mg ratio of 6:2:1, which solved the Sulphate toxicity issue... but which then led to Magnesium deficiency after a period of time. I have now switched to using Calcium carbonate (CaCO3), Potassium bicarbonate (KHCo3), and Calcium Magnesium carbonate (CaMg(CO3)) to get my Ca:K:Mg ratios correct without adding sulphates... and my plants have never looked better... plus my pH is far more stable because of the extra carbonates.

    I've been using a CaCO3 : KHCo3 : CaMg(CO3) ratio of 3:1:3 for a few months now and haven't run into any deficiency issues or lock-out issues... touch wood. Below is a pic of my display as it stands today, the two rows of Oakleaf and Cos lettuce plants towards the rear are less then 4 weeks old.

    I'm also adding Seasol for trace elements, but only 1x capful (15ml) of Seasol per 500L per week.

    My suggestion to you would be to stop adding Maxicrop for a few weeks and when you do resume adding it that you only add 1x capful per fortnight into your 284L. In the meantime I would take a few pics of the plants with the deficiency symptoms, both close up of the individual affected leaves, and wider shots showing the whole plant/s, and post them here so we can try and diagnose your deficiency for you, in case it isn't Potassium.

    Cheers!
     

    Attached Files:

    andyholloway likes this.
  3. Boomking

    Boomking New Member

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    I thought I should add some data about my top up water too. I have taken a few pictures Ill post as well.

    CaCO3 132-241
    Ca 34-63
    Mg 10-19
    Sulfate 37-81
    PH 8.1

    I have been adding Phosphoric acid to the top up water bringing it down to about 6.4. It has taken me quite a few weeks to bring it down to 7.8 from 8.1
     
  4. Boomking

    Boomking New Member

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    Tomato leaf

    Tomato leaf Jpeg.jpg
    Tomato Plant
    Tomato Plant jpeg.jpg
     
  5. Boomking

    Boomking New Member

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  6. Boomking

    Boomking New Member

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    Cucumber Leaf
    Cucumber Leaf.jpg
    Cucumber Plant

    nt cucumber plant.jpg
     
  7. Boomking

    Boomking New Member

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    Spinach Leaf
    spinach leaf.jpg
    Spinach Plant
    spinach plant.jpg
     
  8. Yabbies4me

    Yabbies4me Administrator Staff Member

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    I don't see any Potassium deficiency symptoms in your pics, but you definitely have a Calcium deficiency issue IMO.

    I believe it is due to the high levels of Magnesium from the frequent additions of Epsom salts, and possibly Potassium due to excessive use of Maxicrop.

    My suggestion would be to stop adding anything else at the moment and do 3 or 4 partial water changes of about 20-25% each over the next week. When you top-up during each of the water changes I would make up one of the buckets of top-up water in the following way:

    Fill a 9L bucket with tap water the day before required, drop the pH to 5.0 using Hydrochloric acid (Muriatic acid, pool acid) and maintain it there for 24hrs so all the carbonates are consumed, then raise the pH to about 7.0 using Calcium hydroxide (brickies lime) before adding it to the system.

    After the week of water changes as above I would only top up as required, with tap water treated to a pH of 6.0 with Hydrochloric acid. I would then only add Maxicrop at about 15-20ml every fortnight and focus on getting the plant nutrients into the system through your fish, so use a good quality commercial grade pellet.
     
  9. Boomking

    Boomking New Member

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    So I know better what to look for what is the difference between calcium and potassium deficiency?

    For feed I have been using Hikari Gold baby pellet for goldfish. My system has Shubunkin Goldfish. Is there a better feed you would recommend.
     
  10. Yabbies4me

    Yabbies4me Administrator Staff Member

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    .
    Potassium deficiency tends to occur on the lowest, oldest leaves, while the new growth remains unaffected and healthy. This is because Potassium is a mobile nutrient, meaning if there is a shortage of it the plant can draw it from the older leaves and relocate it to the new growth.

    On most plants it will initially show as pale green or slightly yellow patches between the veins or around the leaf margins. As it progresses the margins and leaf tip will become brown and necrotic, but there will be yellowing behind the edge of the necrotic patches, unlike your spinach plants where there is just necrosis around the margins, but no yellowing behind it or in between the veins on the leaf. As it progresses even further the yellow patches between the veins can become necrotic.

    Calcium deficiency can also show as yellowing between the veins and on the margins on some plants, but that's usually when it's very advanced, and it’s usually near the top or middle of the plant. On most plants well before there is any yellowing there will be deformity of the leaves, especially new growth, as calcium is not a very mobile nutrient. This deformity shows differently on different types of plants, but the most common are cupping and "tip burning" of the new growth. As the new growth is forming the tip and margins of the leaf are affected by slower than normal growth or even necrosis, but the rest of the leaf grows normally so it ends up cupping, or buckling, or folding over the affected areas.
    I will try and find a few pics and post them later.


    As far as fish food is concerned, I've found Gold fish food tends to not have enough nutrients in it for the plants. In my kids little system I alternate between Skretting Nova commercial grade pellets (intended for Trout, Salmon, Perch etc) and the Gold fish food. I alternate because I found if you feed them only the high protein commercial pellets they grow well, look very healthy (bordering on rotund) but just suddenly drop dead with no obvious signs of why... other than an XXL waistline.

    .
     
  11. Boomking

    Boomking New Member

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    I really appreciate you trying to help me. I hope you can help me fix my thinking too. Please don't take this post as argumentative but I am trying to show my rationale so you can tell me where my thought process is flawed. So Maxicrop has a rating of 0-0-1. I believe this means it is 1% potassium so adding in 80 mL gets us down to about 3 ppm of potassium in 284 L of water. The recommendation of potassium for planted aquariums is 10 - 20 ppm.

    1 Tbs of magnesium sulfate every 10 days would be about 6 ppm.

    Calcium seems really high in my top up water. The CaCO3 is 132-241 and Ca is 34-63. The Calcium in my FT water is 60 ppm.

    I am confused on why I would be calcium deficient when I am adding relatively little potassium to the system vs the calcium already present.

    The new growth on my plants (at least to me) looks healthy. The older leaves are scorching at the tips and sometimes dying off. My tomatoes and peas look fantastic (although the peas only have about 4 peas in a pod). No sign of blossom end rot. My pea plant has seemed to stop producing earlier than I would have expected. I am guessing this might be that they are nitrogen sensitive plants and were growing in water that was 60ppm nitrogen until that dropped off.

    Please help me with where my logic is flawed. I appreciate all the experience you guys and gals have to offer.
     
  12. Yabbies4me

    Yabbies4me Administrator Staff Member

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    No, usually those three figures that are on the front label of most liquid, powdered, and granular fertilisers, are simply ratios of the three main elements (NPK) in comparison to each other, not the total percentage of them in the product. Maxicrop’s typical analysis lists the Potassium percentage as about 3.5% from memory.

    I don’t know how you arrived at the 3ppm figure, but let’s use that anyway. Your figure for the total Potassium in the 284L would be correct... after the very first addition... and for each subsequent addition only if your plants used all the Potassium in between each one, but as you are adding that much Maxicrop so frequently you are probably increasing the total Potassium percentage in the 284L with every addition... and, if the total Potassium percentage in the undiluted Maxicrop is actually 3.5x higher than what you thought, these two factors could see the Potassium build up in the system very quickly.

    I’m not saying it’s definitely Potassium that’s making the Calcium unavailable in your system, it could well be the high level of Magnesium...

    If it was actually a Magnesium deficiency your plants had, and the deficiency was simply due to a general lack of Magnesium in the system, then a tablespoon of Potassium sulphate is a LOT more than is required to fix a Magnesium deficiency in your 284L... A level teaspoon into 500L of water well and truly fixes Magnesium deficiency in that situation, and for quite some period of time after that. So adding a tablespoon of it every 10 days, to 284L, has led to a build up of it in the water, which IMO has most likely led to the Calcium in the system not being able to be taken up by the plants.

    Ideally the Ca:Mg ratio should be about 3:1, but yours is the opposite at 1:4... if your measurements/estimates are correct.

    With Ca, K, and Mg, if you have too much of one, the others can’t be taken up by the plant, due to the fact Ca, K, and Mg ions all compete for uptake through the root membrane.

    The older leaves on which plants have tip scorching and are dying off?... Are they yellowing?... because the pics you provided of the Spinach doesn’t show any yellowing or dying off, only necrosis around the margins, but even those affected leaves still look very green.

    Your Tomato plant is not well. It is definitely suffering from a deficiency, and looking at the way the leaves are curling downwards it would suggest Calcium. Deficiencies of the one element can show in different ways on different plants, but the symptoms on your spinach and tomato plants both lead me to believe it’s a Calcium deficiency.

    The new growth may be coming through healthy, as you mentioned (I’m assuming we were talking about the spinach there) because Calcium has become available to the plant at the time those leaves were forming, ie: possibly some considerable time after you added the last dose of Magnesium and possibly just topped up with Calcium rich water, which also diluted the Magnesium... just spitballing here.

    The Spinach leaves with the necrosis around the margins, did they form that way from new, or were they healthy at first then developed the necrosis much later?

    I going to be honest... I know a lot of people find it very interesting, but of the people I’ve seen that test every single aspect of their AP water, including individual elements, most of them tend to have very frequent or ongoing issues with nutrient deficiencies, more so than those that don’t test. They tend to over analyse then chase their own tails around trying to achieve certain concentrations, of particular nutrients, that supposedly work “on paper”, or “in theory”, but not in the real world, especially the aquaponic world.

    I have a long background in hydroponics, where you can deal in absolutes much of the time in regards to nutrients, especially for mono-culture in controlled conditions... but aquaponics is an entirely different kettle of fish (or IBC of fish), especially on the small scale of most backyard or indoor enthusiasts systems. The organic nature of aquaponic systems throws more many variables into the equation.

    I’ve been into aquaponics for quite some time now, both personally and through the store. I also offer a consultancy service where I go out and look at customers systems and help them with issues, but I have never once tested individual nutrients in any aquaponic system, and I’ve only ever tested the water hardness in one of my systems once, out of curiosity basically... and I have never run into any major nutrient deficiencies.

    Don’t get me wrong, I have had, and still do get deficiencies occasionally, but I catch them early and take specific, targeted action to rectify them, I find this is the best method for aquaponics. For the Ca and Mg deficiencies I’ve had, in just about every case they were brought about by using too much Potassium bicarbonate in ratio to the two others while trying to maintain/raise/buffer my system pH.

    Again, my suggestion would be to do a few partial water changes to dilute down what’s already in there, get a little Calcium into the system as I described a few posts back (unless the new growth on all your plants is fine), then go back to basics... ie: feed the fish a good quality feed, add a capful of maxicrop every 1-2 weeks for your 284L, monitor the pH weekly... and avoid testing individual nutrient levels, avoid trying to figure out exactly what’s in your system and exactly what you need to add... you’ll never get it spot on in aquaponics, especially in such a small system, and you’ll end up chasing your own tail around in ever decreasing circles until your head disappears up your own...

    The K.I.S.S. principle works well in aquaponics, and will save your sanity.

    Just my opinion...

    Cheers!
    .
     
  13. Murray

    Murray Site Admin Staff Member

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    In the US there is available Maxicrop with fish emulsion.
    See here. http://www.maxicrop.com/pages/application_guidelines.html#liquidSeaweedFish
    They do not have very good analysis of their product on line. Perhaps you will need to go to a store somewhere and take a look at the label. Have had many sing the praises of the "seaweed with fish" product for use in Aquaponics.
    I am not sure if the Australian version of Maxicrop is the same analysis as the US product.
     
  14. Ringer

    Ringer Active Member

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    Hi Boomking,
    Good advice I reckon !
    Water is almost never just water its a chemical cocktail , and unfortunately we can't analyse or control every specific "nutrient" in our water . The tests readily available to us (Ph, nitrate and ammonia )give us a vague overview of what's going on at best. It's very difficult to control or sometimes even understand the effects one amount of nutrient has on another or their combined effects at different levels on our plants. I test and try to control Ph , and I only test for nitrate,nitrites and ammonia to monitor my bacterial efficiency and that's it (doing some hardness experiments but that's another story). When I first started I wanted to measure and control every aspect of my water chemistry. A smart man once told me the best method is to be reactive and if you have an issue then specifically treat it , this turned out to be very sound advice.
    Here's an analogy I use , if you add X to your water your Y will react and adjust . Then when the X you added is depleted your Y is out of balance . So now two variables that are out of balance. Things can get really complicated really fast.
    The point I'm trying to make is if you feed quality food to your fish maintain a neutral Ph (7 to 7.4) and have a healthy bacterial colony the rest pretty much takes care of itself with little need for intervention. Maxicrop and seasol can then help supplement any deficencies that occur. I only use it (Maxicrop) as a folic spray so I can't accidentally overdose my plants or unbalance my bacterial colony , my fish don't need it either (my choice).
    If I see a change in my leaves I then use dilute maxicrop , I use it at 8ml per litre and spray on to the leaves just till they drip and only at night . Two nights later I spray the leaves again with just water to fluidise any residual nutrients making them avaiable to the plants again. And that's about all I do. Natural processes do the rest , too easy.
    Hope that helps.
     
    Last edited: Jun 3, 2016

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