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I've had my system for about 6 months and everything was going good. Suddenly a couple of weeks ago I had a few dead fish, and now I'm getting about one a day. I'm down from 30 to 10 Tilapia.

I have a 350 gallon tank and a 300 gallon tank with two fingerlings in it. My running a CHOP2 system with auto siphons in 3 IBC grow beds. The water temp is between 65 and 70 and the entire system is in a greenhouse and I have a couple of black 55 gallon water tanks working as a heat sink to keep the temp up during the night.

I don't have a filter but use a slo to dump the waste into the sump tank and I've been cleaning it out with a wet vac. When I got the dead fish My Ammonia level was about 50 ppm, and the Nitrates were between 20 and 40 PPM. My PH was about 7.4.

I stopped feeding the fish and haven't fed them since. I've done about a dozen 60% water exchanges with my well water (ph about 8.2) and the ammonia and nitrate level hasn't changed and stays the same even when I check it right after a water exchange.

About a month before they started dying I put some cinder blocks in the fish tank to help support the 4x4s holding up the grow beds as they were sagging and pushing down on the fish tank. I had read that they might change PH, but was adjusting it with phosphoric acid and it was stable. I've since read that cinder blocks are made with 30% fly ash which contains heavy metals and arsenic, so I pulled them out a couple of days ago.

Also a couple of months ago I added some worms to the grow beds to help eat the solids. This past week I pulled out the green bean plant that was looking a little sad as I read that they create nitrates. This last week I've also planted a couple dozen broccoli and cauliflower plants, and a dozen lettuce plants as well. I have a tomato plant growing like crazy and a few more plants to help eat up the fish waste.

I've also tried to hook up a solids filter using a 5 gallon bucket, but it keeps overflowing after the grow beds dump out a few times.

Why are my nitrate and ammonia levels remaining so high? Do I need to pull my plants and wash my grow beds and media and replant them? Did I poison my fish? How can I get my system back on track? I thought that after 6 months it was supposed to be all settled in.


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You do, in fact have a filter since gravel growbeds function as bio and mechanical filters.  I think what you mean is that you do not filter solids prior to the growbeds, which is a very common practice and generally not a problem.

The nitrate level is irrelevant and it's likely that nitrite killed your fish.  Usually, this is done before a problem, rather than after, but you may be able to mitigate nitrite damage by salting, the normal dosage being one kilo of non-iodized salt per 1000 liters of water.  I'm no expert on this subject so be sure to search this site for more information.

If you read START HERE/RULES OF THUMB on this site, you will see that ammonia and nitrite levels should be no greater than .75 ppm.  What I suspect may have happened to your system is the PH was allowed to go down too far and then your bacteria population crashed, resulting in high ammonia and nitrite.  In a normally functioning aquaponics system, nitrification drives down PH so it's unusual that PH would need to be adjusted down, instead of up.

The water changes you are doing should be changing the test results.  Read the testing directions carefully.  

Good luck

Thanks for the feedback!Your correct, I did mean that I'm not filtering the solids prior to the grow beds.  I'll go and look up the salting and the rules of thumb. The water here is pretty high PH, we had to put in a water softener and use RO to our well water to cook with in the house. We live in Texas hill country and whenever I dig in the yard I pull up Oyster, clam and seashell fossils, not to mention super high PH rock is more present than soil.

Have you had your water tested? I was using cistern water in my system and discovered that I had .013 ml of zinc in the water. That was enough to start killing fish after about 3 months. And, just like you, they were dying regularly. I'd strongly suggest you have the water tested, if you haven't already. BTW, I had tried EVERYTHING else before I discovered the problem. 

Not a bad idea! Where did you go to get your water tested?

I did it online with a national company. I think they are called National Labs. Do a search on water testing. It costs about 100 bucks but is well, well worth it. 


Looks like your getting some really good feedback, I'll add one observation, from looking at your pictures you have some wood over the top of your tank, hopefully its not treated lumber, there are some real nasty things in the chemistry used in the treating process and a small ecosystem would have a hard time dealing with direct or even occasional contact from condensation dripping back into your tank.    The link I've added has some really good info on the subject.

Good luck,



I'll look up that lab and send them a water sample.


I used bare cedar locally available, I was afraid that the arsenic treaded lumber would leech into the water somehow. I'll check out the link for more info on it.

I really wish that I had used regular IBC totes for the fish tank like most everyone else did. It would have made mounting my grow beds so much easier! The lady from the aquaponic source really talked up round tanks so I went that route. I also sank my sump down in the ground to try and regulate the water temperature, but that has added problems as well. Live and learn I guess.

I've heard that with an ammonia/Nitrite problem that won't go away there may be something dead in your tank (fish maybe) and the decaying would produce ammonia. 

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