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

Nitrites and high nitrates

Discussion in 'Water Chemistry' started by stimson, Jan 18, 2012.

  1. stimson

    stimson New Member

    Joined:
    Feb 27, 2011
    Messages:
    18
    My system has been running for nearly 12 months now.
    I have a 300L fish tank with 15 jade perch (approx 200mm long) and 10 silvers (approx 120mm long).
    2 x Grow beds at 300L and 500L.
    Plants are growing very well.

    Ph around 6.6-6.4.
    Amm 0.0
    water temp around 26deg

    Problem is
    Nitrites are at 0.25 - 0.5
    Nitrates are at 140-160 alot of the time

    I figured I must now have too many big fish for my system to keep up with using the nitrates and the nitrites are backing up.

    What you all reckon? Start eating fish?
     
  2. RupertofOZ

    RupertofOZ New Member

    Joined:
    Jun 15, 2009
    Messages:
    5,569
    Nope.... you don't have enough plants to use up the nitrates....

    But the high nitrate reading, in conjunction with nitrtie reading... suggests that you're over-stocked, or under-filtered... basically, that your system is tottering on the edge of imbalance...

    On the face of it.... your number of fish... for volume of grow bed filtration appears OK... but that many fish in a small volume (300L).... may mean that you're not turning your water over enough... and nitrifying the ammonia fast enough....

    Do you have a constant battle with pH falling to 6.0, or below... requiring buffering??

    Really, if you think about it... 25 growing fish in a 300L tank... is a bit like putting a fish in a 10L bucket... and like battery hen farming...

    You could also be short of air... both for the fish... but particularly for nitrification... especially as a 300L tank will warm quickly....

    If you don't have already... with that many fish in that tank... growing... I'd invest in an airpump... and a battery backup airpump, or failover system...
     
    Last edited: Jan 18, 2012
  3. Yabbies4me

    Yabbies4me Administrator Staff Member

    Joined:
    Jul 27, 2010
    Messages:
    5,881
    Country:
    Australia
    State:
    W.A.
    City:
    Perth
    Definitely too many fish IMO... 30 per 1000L is a safe stocking density and will still provide good plant growth.

    Your GB:FT ratio is well over 2:1 and you are still getting High N02 & N03... too many fish... or not enough plants as Rupe said, are your GB's full of plants?

    Although, I would've thought insufficient quantity of plants would've resulted in just high N03 if the filtration capacity was large enough, which yours appears to be.

    Cheers, Yabbies.
    .
     
    Last edited: Jan 18, 2012
  4. RupertofOZ

    RupertofOZ New Member

    Joined:
    Jun 15, 2009
    Messages:
    5,569
    I was editing... as you posted Yabbies...

    More issues relating to nitrification and oxygenation... basically too many fish... not so much for the available filtration... but for the size of the tank...
     
  5. Yabbies4me

    Yabbies4me Administrator Staff Member

    Joined:
    Jul 27, 2010
    Messages:
    5,881
    Country:
    Australia
    State:
    W.A.
    City:
    Perth
    :trout:......
     
  6. stimson

    stimson New Member

    Joined:
    Feb 27, 2011
    Messages:
    18
    yes, I have grow beds overflowing with plants, even gone horizontal with watermellon and cucumbers.

    Yes, have airstone in fish tank and a battery backup running both pump and airstones.
    Running a 2000L/hr water pump

    At the moment I am having to buffer up every week.

    When i purchased my fish from the hatchery you could only get minimum $50 worth of fingerlings. So that is what I did. Only 5 died out of them.

    I have been thinking of either harvesting the couple of bigger ones and transferring some to my sister inlaws system who is just about cycled. I was thinking around the 10-12 mark for fish would probably be better.

    I would like to install another grow bed but am pushed for space as I have only on a small back yard.
     
  7. RupertofOZ

    RupertofOZ New Member

    Joined:
    Jun 15, 2009
    Messages:
    5,569
    Trace ammonia and nitrites... high nitrates... constant pH drift, and buffering...

    Everything is saying... too many fish... for the volume of water...
     
  8. MoeCanada

    MoeCanada Member

    Joined:
    Nov 19, 2010
    Messages:
    155
    Do you have solid/Sludge removal filter. Something like an external biofilter or swirl filter. I would install an additional solid/Sludge removal filter as any decomposing solids in the system would produce excess nitrates and reduce oxygen.

    One more thing is it flood/ drain set up, constant flow or are you using any kind of timer.

    I have currently 45 bluegill 5-6 " long in a 100 gallon fish tank with 4 air stones and 950 gallons/hour pump with three grow beds. System has been running for almost two months with less than 10ppm nitrates, 0 ammonia, o nitrite but the only thing iam doing different than you is removing solids from the system.

    under a heavy fish load if you remove solids then your system will have a much better balance.
     
  9. tpilk

    tpilk Super Moderator

    Joined:
    Aug 9, 2011
    Messages:
    500
    You guys are playing with fire. One little slip and you could lose them all. The guys that are pushing max density are doing it in 20,000L FT's or similar, with all the appropriate equipment. You both have very limited capacity at 100Gal and 80Gal, no safety margin - things just happen too quickly. IMHO, time for either a BBQ or an investment.
     
  10. stimson

    stimson New Member

    Joined:
    Feb 27, 2011
    Messages:
    18
    No swirl filter, my water quality is fine - clear as.

    I am running flood and drain with bell syphons.

    Going to reduce the fish numbers. Will get onto it this weekend.
     
  11. rmcpb

    rmcpb New Member

    Joined:
    Jul 1, 2010
    Messages:
    181
    It would be quite simple to put a pad of filter medium under each inlet to a GB and rinse it daily. As mentioned removing the solids will help relieve the load on the system and its a relatively simple thing to do.
     

Share This Page