I have a 4000 gallon system with two concrete fish tanks, an 100 gallon upflow biofilter, 100 sq ft of vegetable grow bed and a 100 gallon sump. It is a recirculating system known as an aquaponics system. Bacteria in the biofilter convert ammonia to nitrite, then nitrate, which the vegs eat, then the water returns to the fish.
I stocked 525 fish: 250 hybrid blue gill, 200 channel catfish, 50 yellow perch and 25 hybrid stripped bass. The concrete tanks were new and leeched alkaline to the water raising pH to 8.5. The fish from Jones hatchery were from pH 7.2 water. About 5 days after getting the fish,they started dying. I lost all the bass and perch before I could get the pH to 7.6 with white vinegar. Then with the pH steady, the fish eat well and gained weight. Three weeks later they stopped eating and the catfish started dying in large numbers (dozen a day). The ammonia tests at 0.0ppm, nitrite at 0.1ppm, pH at 7.8. I do not see any problems visually on the freshly dead or dying fish. I put high resolution pictures of the fish & tank at my web site (www.thebasbergs.com) under photo album/greenhouse/sick fish. (See Fish)
I really need some help. I do not know what to test for or do to solve my problem.
Any suggestions would be greatly appreciated. Rob at Jones hatchery said the best chance would be advice from this forum...hope he is right.

Thanks, Doug

{Note: I added a link to Doug's photo album. -Theo}

Welcome, Doug.

Sorry to hear about your problem.

The first thing I'd do is test the DO (dissolved oxygen). I've seen a couple of aquaponic systems that were devoid of oxygen, or close to it.

Rule #1 of fish culture is: If your fish are dying, and they're wet, check the oxygen.

I have no idea Doug, but hopefully someone will chime in here shortly. My first thoughts are to ask what you are feeding your fish as old pellets can go bad. Are the water temps high due to the copper/solar fish tank heater exchange?

Here is the link to your web page regarding the fish so others can access it easily.
http://thebasbergs.com/thebasbergs/sick_fish.htm

I have some experience in home aquariums, but my largest tank is only a 125 gallon. Nothing to match your 4000 gallons. However, I do have some input to your problems.

The first thing I noticed when reading your post was your ammonia and nitrite tests. 0 ppm ammonia is good, but in a stable tank, NITRITES should be at 0, and NITRATES are the only thing that should be in your water. Nitrates themselves in low numbers are good because they cut down your fish waste, and mean that your tank has fully cycled. However, if your water is not changed enough, and fish waste is just left to sit, they can accumulate over enough time and high numbers of NITRATES can easily kill your fish. Anything smaller than a decent sized pond is not self-sustaining and does need to be taken care of.

Please do a test on NITRATES and post your findings here. Your tank may not be fully cycled, or is and the water isnt be changed enough.

The second thing I noticed was that you didnt mention if you had conditioned the water to get rid of the chloramine and chlorine if you used tap water prior to introducing the fish. Both can kill your fish as the chemicals eat away at the gills.

Bruce is right on about the oxygen. With that high of a fish load, oxygen is a worry.


"New Tank Syndrome" is the common term that aquarists use for situations similar to this. Maybe I can find some links that explain cycling, and ammonia, nitrites, and nitrates better than I can.

- Jighead

These may help. The water quality ones explain ammonia and the N matters noted above.

SRAC 450-459; 4500-4599 -- Recirculating Systems
http://srac.tamu.edu/index.cfm?catid=24


SRAC 460-471; 4600-4699 -- Water Quality
http://srac.tamu.edu/index.cfm?catid=25

I found the article I was looking for. This article describes ammonia, nitrites, and nitrates relating to fish in the best way that I have seen so far. Start by reading "What do we mean by Cycling" and browse from there.


Take a look: http://www.aquariumboard.com/forums/articles/26.htm


- Jighead

This article tells of the importance of water changes, and how ammonia, nitrites, and nitrates are effected by them. A shorter read than the last article, but still a lot of information. Check it out: http://www.aquariumboard.com/forums/articles/4802.htm


- Jighead

Thank you for the quick response...most appreciated.
More facts. I have a Milwaukee DO meter. I measure regularly. It reads 7 now. When I had anearobic sludge on the bottom, it read 5.5. The water temp has been 68-72F. I do not have a nitrate testkit; I will buy one tomorrow. I did a cycle on my tank with ammonia. Starting at 6ppm, it took 5 weeks in April to get to 0.0ppm. The nitrite went to 5ppm after the ammonia started dropping. The nitrite now reads 0.1ppm or less (0.1 is smallest the test kit measures.
I will start reading the references you have provided. Your help is greatly appreciated.
After the waste started building up on the bottom, I installed an old pool sand filter and did three vacuumings of the bottom to waste. The water looks good now, but was full of particles a week ago for about 6 days until I could get the sand filter installed. I have zeolite in the sand filter.
Any other ideas will also be appreciated.
Thanks again.
Doug

Doug,

How about contacting Steven VanGorder at

altaqua@ptd.net

He an excellent book out called small scale aquaculture where he covers a chapter on Aquaponics. He's also well versed in RAS'.

Doug - Are you only losing the catfish. No other deaths? Are the other fish still eating food?

I am just an amateur at this but aren't Catfish bottom feeders and thus a bottom sludge issue may be causing the toxic reaction. Like Glycol it tastes good until it starts to take effect.
Just a thought.

Sam,

How large are the fish? 8 gallons per fish sounds like pushing the envelope. I realize you are doing all the right things to detoxify the wastes. What are the stocking recommendations for this type system? The water seems a bit cool for the CC to be taking many pellets. Without much natural food being produced...well. I would try a slowly sinking feed, and/or start culling the less vigorous fish.

Have the catfish deaths stopped? Catfish are documented territorial - pecking order fish and to minimize fighting in confined spaces they have to be held at certain densities per cubic foot. Possibly your stocking densities for the catfish are too low.

Catfish can be bottom feeders or feed pelagically, but they do not eat sludge and dead aged materials comprising the bottom sediments. "Bottom feeding" most often means feeding on living organisms associated with the bottom areas. In the case of omnivores some of the consumed materials can be fresh dead materials usually animal origin and occasionally plant materials.

quote Cody "Possibly your stocking densities for the catfish are too low" ?

Isn't the ratio of hydroponic plants to gallons of fish tank usually higher than 100 sq ft to 4000?

Not sure where that might go, just something I noted...

DB has 4 species of fish in 4000 gal. Depending on how many CC he has in his one or two tanks, the density of CC may not be high enough to prevent fighting. Catfish in cages and tanks need to be at a certain density or fighting and deaths will occur. DB is probably not frequenting this site much after his initial query, thus we may not find out how things are currently going on in his aquaculture system. I think one of his initial problems was using polyculture as a beginner.

I think I get it, Bill. If they are very, very crowded, then no room to be territorial. If crowded, but not to an extreme extent, then they will cause harm to each other. That is very interesting. Do you have a reference that I can look to for further insight?

thanks.

Firstly You should check your water quality, Second is that should be used tap water because tap water should be airatted for 48 hours due to chlorine. You should run a your system for 10 days with cheap fish in it. To get your Bacteria going and You can follow some steps
1. Seperate the larger ones from the smaller ones.
2. Cover the tank with something that will exclude the predator.
3. Hide and wait till the person strikes and catch them in the act.
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