How Ammonia Works In Your System

We’ll begin with a normally operating organic aquaponics system that we use calcium carbonate in for adjusting pH. In such a system, your ammonia and nitrite levels will vary from 0.25 to 1 ppm; and your nitrate level will vary from 1 to 10 ppm (with occasional periods lasting months in which nitrates are not measurable at all, but the vegetables just keep growing explosively!). As your fish get bigger, it’s tempting to feed them more, so you do. What you will notice at some point is that, as a result of feeding your fish more, and them generating more fish poop, your system ammonia level will begin rising (from its normal range of 0.25 to 1 ppm) up to 2 ppm, then 3 ppm, and so on.

(Below) Lifegard ammonia test strips, accurate down to 0.5 ppm.

This is happening because your limited number of bacteria do not have an unlimited ability to process ammonia into nitrites and then into nitrates! When more ammonia shows up in the system than they can metabolize and convert, you have simply overwhelmed the ability of your bacteria to process ammonia and the ammonia level will continue to rise until you do something to stop it, such as feeding your fish less.

Although your system will work fine with a very small amount of fish, if you have too many fish and/or feed them too much, your ammonia level will rise. Fortunately, there’s a simple solution to this problem: stop feeding them so much! You can easily go from feeding your fish three times a day to once. If that doesn’t do it, feed them once every other day. After a week to two of feeding the fish less, you will notice the ammonia level coming down from 3 ppm to 2, then to 1, which is where it should be.

The amount you feed the fish controls your ammonia level. This is totally logical: more fish food in, more fish poop and ammonia out, regardless of the number of fish involved. They may get irritated if fed less, but it won’t kill them; fish are not like people in this respect. We’ve omitted feeding our tilapia for up to a three weeks at a time with no ill effects except they splash like crazy and soak the “feeder person” when they finally are fed!

When the situation becomes too extreme, as when you are feeding your fish every third day, but the ammonia level is still rising, you need to sell some fish. Sell half of them and get them out of your system! Although you can’t grow fish at a profit (you lose money, remember?), your fish will still get bigger and bigger until you have too many pounds of fish and too much ammonia. This is the indicator that it’s time to sell fish; this creates cash flow too! Selling fish will help pay for the expense of raising them to be your “fertilizer generator”.

There is one more thing you should know: overfeeding the fish is not the only way to clobber your system with too much ammonia. If you have any other source of decaying organic material in your system, it will give off ammonia as part of the decay process. If your ammonia is rising quickly, look for dead stuff, such as a dead fish caught in a pipe, or a huge mass of roots or other vegetable material that a careless employee dumped into a trough instead of removing (see photo above).