Backyard Aquaponics
A place to discuss aquaponics

Seperate a few if you can and see how they fair?

20gal fish tank with typical filtration could handle 2 cats absolute tops. One would be better.

What does the biologist say? Or is it a moot point now?

Hi Doug, sorry about the issues!

If they're sick and they look healthy maybe it will run its course. I had all my goldfish die last year and they looked great, which was very frustrating. My plants grew like crazy as the fish all died.

Is your fish tank very deep? How does oxygen get to the bottom? Does the water turn over enough to circulate oxygen all around? Could the dead fish debris from earlier have given the catfish some disease?

Are neighboring farmers spraying any pesticides or herbicides?

Janet, the biologist thinks they have a bacterial infection or a protozoan parasite from being stressed by pH, water quality, or both. With AP, the medicines normally used to fight disease would be ruled out unless I have a quarantine tank. He suggested I post at pondboss.com to get advice and I am trying that. He also said he did not have experience with recirculating systems.

Dave my water depth is 42". I have two 12" air stones on the bottom running about 2 cfm. This moves water up from bottom and creates a circular current as well. I can drop food at one point and it circles the tank as they feed. It may well be that the dead fish stayed in the tank too long when the water was murky and I could not see the bottom. That may have lead to the catfish getting a disease (they are bottom fish and scavengers). That was the fish biologist's thinking too.

The water is clean looking now and I can see the bottom. I take dead fish out as soon as I see them (even a few not quit dead yet ). It sure ran thru the population thoroughly! This is the Ebola of fish world.

I will make the best of things...so now I have a monoculture of hybrid blue gill (approx 150) that I will try to keep healthy. Next spring I will probably try the same four species again. I really want to compare them for what is best, once the system is stable and clean.

Hang in there DB..... your experience will ultimately not only benefit yourself but those that follow

The "scum" on the surface could be the protective mucous of the fish' being sloughed off which would support the biologists theory of a bacterial infection or protazoan parisite, however the very red vent and red fins is sometimes a sign on severe ammonia burn (as well as other things)
it sounds as though the water is pretty well mixed, but is it possible that there is a layer of high ammonia water right on the bottom of the tank (Which would result if there was a buildup of wastes on the bottom without the water being circulated much..)?

If it is a protazoan parasite, will the bluegill remain as hosts and therefore keep the parasite in your system and possibly create problems again in the future. Or are these always present and only become an issue when fish run down??

i believe most diseases are always present and only manifest themselves when the fish are stressed, some can be killed out , but others cant be killed without killing the fish

Well, 3ppt salt it is then. If you're willing to sacrifice some/all plants, you could go higher on the salt, but I don't know the tolerances for bluegill and catfish.

I will add the salt at 2ppt to start, then 3ppt after a while (perhaps the plants can adjust with time?). I will let you know about how the bluegill do.

I am reading the literature (books) I already have. One is a hugh volume on RAS (recirc aquaculture systems). It says many commercial ventures fail due to 'fines' (1-10micron particles). Your flood and drain filters them out. My deep water system does not. They choke the fish, so you have dead fish that have no blemishes...sounds familiar. They also say that fines are hard to remove. Sand filters work down to 20microns. I think I will contact Dr. Savidov to see if this could be my problem/how to detect if it is/how to fix it. I will let you know.

BTW, besides keeping the forum informed, I will be publishing my experiences in 'Aquaponics Journal'. There is often more to learn from trouble than from pure success.

Oh, next question...how do I calculate how much salt per 1000 gallons for 1ppt? Liquid to liquid dilution is easy, but a solid in a liquid is tougher. Something about molecular weight and moles??

Next, next question...is there a way to measure the salt concentration in the water? I can do titration, but do not want to buy more meters if possible.
Test kit? Available in fish stores?

doug, read from this page onwards.........discussion over the last two days

http://backyardaquaponics.com/forum/vie ... &start=210

1) Go metric: 1 gram of salt mixed with 1 liter (1000 grams) of water is 1
part per thousand. And remember to get UNIODIZED salt.

2) Yes, there are salinity test kits. Drops-n-test-tube things.

Excellent Steve. Just what I needed. My wife is picking up a nitrate and a salinity test kit for me at Pet Supply Plus today.

The hydrometer chart says at 21C, 2.4ppt=1.001 & 3.7ppt=1.002 pretty small increment! Or am I reading it wrong? I would like to use the hydrometer but that seems pretty inaccurate with those numbers. Is anyone on the forum using the hydrometer?

Thanks Janet...so grams are grams..solid or liquid. Hudah thunk?

4000gallonsX3.78l/gx3ppt=45,360grams/454=99.91 pounds of salt....wow! Someone check my math before I brine preserve my remaining fish! 100 pounds of salt???