Aquaponic Gardening

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I have a 300 gallon tank with koi, goldfish and a few cat fish. at total of about 15 fish....just recently a few koi died. I tested the water and the the Nitrate was the only thing that was high(80ppm)....Is this too high of Nitrate level?? what can I do to lower the Nitrate if I have to?....My system is less than 2 years old....any advice, comments or tips would be greatly appreciated! Thank you!

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So you increased the amount of feed with the rising temperatures?? It is hard to know for sure without more information. However, with increased feed your fish you are increasing the amounts of ammonia in your system. The ammonia is toxic to fish, however, nitrifying bacteria converts the ammonia into nitrite. Nitrite is toxic to fish as well. From here the bacteria converts the nitrite into nitrate. Nitrate is what your plants love and are taking up and it is much less harmful to fish. Nitrate must be at very high levels to become toxic.

So with all of that being said you probably had some ammonia or nitrite spikes from the increased feed that killed the fish. Also with the increased temperature the ammonia becomes more toxic to your fish....

I actually just wrote a short article on some useful facts for water chemistry. I posted it on this site but here is the link here as well if you are interested. It goes a little more in depth of what I just talked about.

Water Chemistry:


Also, you may be interested in this information on the nitrogen cycle in your aquaponics system:

  What i started doing NOW (I know right) is taking down accurate notes on temps, levels and every thing else i that i will be doing to fix this problem........From asking around this is the conclusion that I came to. As soon as spring came around the weather got a little warmer I started feeding my fish 2-3x a day. Thus creating extra or too much waste(nitrate)?? Im just a beginner and this is just my guess. The solution to my guess is to start feeding the fish once a day and once every 2 weeks exchange 10 gallons of "fish water" with fresh water.....

What is your ph? what is your kh?

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