Backyard Aquaponics
A place to discuss aquaponics

Hi all,

I've had my channel cats now for about four months. During that time it has been cold and rainy almost every day and though they haven't grown very much, they have seemed happy and healthy and I think I've only lost one until recently.

Over the last few days, the temperature has warmed up quite a bit and the water temp, which has been hovering around 45-50 degrees F, is now up over 60. I was expecting the fish to get more active and eat more as the water warmed but I'm finding that I'm losing a couple every day for the last few days.

Most of them still seem really healthy, but I see the occasional fish listing on its side or back and then righting itself and swimming away. Then I come home from work and find it dead.

My levels are:

Ammonia = 0
Nitrites = 0
Nitrates = Somewhere in the dark red spectrum on the test kit
PH = Around 7.8

I'm running a Venturi T and though I don't have a D.O. tester, I've got a lot of bubbles happening so I think I should be fine there.

I'm not sure if this is just a natural selection process and I should expect some to die off or if I've got a bigger problem going on. It seems to be the smallest of the bunch that are making their way to the great pond in the sky.

Thanks for any advice.

Sorry to hear about the fish Scooter.

The water is still cool enough that Dissolved Oxygen probably isn't the problem unless you're way overstocked. It would be good to know more about your system and maybe have some pics.

It's pretty difficult to tell what's going on at this point (and we may never know with or without lab tests ). It could be that there was an ammonia or nitrite spike which did some damage and you're just seeing the results now. Fish frequently die off like this after a spike. Another possibility is the fish have an internal infection that you can't see - especially for younger catfish, temps around the 60 degree area can be a problem. As the temp warms you'll probably see fewer deaths if this is what's going on. On the other hand if the temp goes back and forth across this temperature zone or remains in this zone you'll probably see more deaths. This link will tell you more about one type of disease that causes this scenario - Enteric Septicemia of Catfish (ESC) but it's important to note that signs are not always as obvious as in the pictures - http://www.aces.edu/dept/fisheries/aquaculture/documents/EntericSepticemiaofCatfish.pdf. The fish may have already been infected when you got them but with the warmer temps the organism becomes active.

One of those two scenarios is my best guess.

Scotty, good paper, good information.

One interesting note is that it is mentioned at least twice that low chloride/low saline water helps ESC specifically along.

Seems like salting to 2ppt or more should be done immediately in this case, unless it has already been done. Salting would help with either ESC or nitrite spikes. no help for established damage from high levels, though.

Sounds like a good idea based on this as well - http://www.int-res.com/articles/dao/21/d021p171.pdf

If I read the first part correctly, infections never occur in waters that are at 2.5 ppt (ppt is parts per thousand in this case). I wouldn't want to keep a system there for a real long time because the plants would gradually start to suffer but I think it's a good idea if it looks likely that ESC is potentially responsible since mortalities were reduced.

Ich lifecycle speeds up at warmer temps and salt would help that too.

Wow! What a wealth of information. Thanks you guys for the articles and the suggestions!

I'm not sure if ESC is what is going on, but it sounds like that may be it. I'm pretty sure that I didn't have an ammonia or nitrite spike as I check the water pretty regularly.

In any case, I'll salt the water today and see what that does for the situation. Hopefully the plants will tolerate it for awhile.

I'll keep you posted and try to send some pictures of my system soon.

Thanks. again.

Let me ask you guys this.

My system holds about 900 gallons total (300 gal. fish tank and 3 180 gal grow beds + 55 gallon swirl filter, sump, etc. By my calculations 2 parts per thousand is about 29 cups of salt. That seems like an awful lot of salt to be putting into a system that is growing plants.

I'm wondering what you think about putting all of my fish (about 90 2" long fingerlings) into a 5 gallon bucket with 2 ppt salt in it. Thus saving my plants and saving myself from having to buy so much salt.

Also, if I did that, how long should I keep the fish in there before returning them to the tank?

Incidentally, yesterday I found a fish that was more dead than alive and stuck it in a plastic tub in which I had dissolved some kitchen salt in some fish tank water. I have no idea what the ratio was. I expected to find it dead today but instead found it swimming around so the salt thing seems to be helping.

thanks.

Should be around 15 lbs assuming there isn't already salt in the system.

I'd just salt the system. There was mention of this bacteria surviving in sediments and Edwarsiella is relatively common in nature - part of the same group as E. coli, Salmonella and others.

Okay! here goes. Thanks.

Hi Scotty.

I salted my system over the weekend and the fish seem to be doing alright so far. I'll see over the next few days if the mortality rate decreases. If it were you, how long would you leave the system alone before you start diluting the water back to normal. A week? Two weeks?

Just curious. Thanks.

Good question and I'm not sure what to tell you . I don't think the salt treatment kills the bacteria that causes ESC but it probably inhibits it's growth. We know that younger fish are more susceptible and we know that at higher temps this is less of a problem. I would hold the higher salt concentrations until the water warms up out of the temperature danger zone. By the end of summer, I'm thinking that the fish will have grown enough they'll be less susceptible but you might have to salt again. There are no guarantees that this will work but that's what I would do.

I'm not sure how your system is setup but you could increase the temperature using a hoop house over the system. Catfish like warmer temps and I think the cooler water makes them more susceptible to this sort of thing.

thanks Scotty.

I already have the whole system under a hoop house so hopefully it'll warm up enough soon.

I believe the consensus is that most plants will tolerate >2ppt. Strawberries are the frequently named exception.
Scotty's 15lbs is bang on 2ppt, if that's what you are running, I would not deliberately dilute. Just let the salt gradually decrease if you ever do water changes, or filter flushes. The fish will always be happier in the salted water. I found one link that says channel cats prefer less than 4 ppt salinity, but will survive up to 11 ppt.

Thanks for that Gingerbread Man.

I added 15 lbs and have lost about 15 more fish since then. There are some that are still looking lethargic but none dead today and still a significant number looking healthy so I'm optimistic that they're rounding the corner.

Sorry to hear about the other fish but can't say that I'm surprised . I had one go of Channel Catfish, almost 50 fingerlings, where only about 6 survived. I think in my climate (cool) it's worth getting the catfish when they are a bit older and a little over 6 inches. This is one disease that should respond to antibiotics (assuming any are approved) but antibiotics could present problems in an AP setup because of the biofilter. FWIW, Bluegill in the same tank, no problems, I've only lost one.