winter catfish die-off

[Dan Ponton]

Last winter and again this winter my catfish stop eating almost completely. Last winter I lost about 6-8 due to starvation as far as I can tell. this winter I just lost my second catfish. Most of the food goes uneaten and lays on the bottom until I remove it. I do not heat the water and at times it will be 45 degrees.

Is this typical for catfish?

[TCLynx]

Fish being cold blooded will experience a slow time in their metabolism when the temperature is too low for them.

Basically this means that they will slow their feeding as the temperature drops and when it gets too cold they will quit eating.  If they are not eating the feed, don't offer them so much.

In my systems I reduce feed as the water temperature gets below 65 F and by the time the water is below 55 F I'm not feeding mine much at all.  At 45 F I definitely would not be feeding the fish.

(Take note that you generally stop feeding tilapia when the water is below 70 F and the tilapia are in danger of dieing when the water gets down below 50-55 F)

Catfish, as long as they are big enough to survive not eating for an extended time, can survive water down near freezing.  However, they can't survive the water temperature swinging too fast.  It is natural for them to experience a slow cool down of the water and basically be at a slow almost hibernating state through winter.  It is not natural for them to experience daytime temperatures in the mind 60's and night time temperatures in the mid 40's where the water temp is swinging more than 10 F between day and night.  That kind of stress can weaken the fish as well as cause them to be over fed for the temperatures they are experiencing and could cause deaths.  These kinds of temperature swings happening too often are a sign that your fish tank volume isn't big enough for the environment without some form of temperature mitigation. 

If the water is too cool, don't feed your fish, uneaten feed in the tank and the stress of having a net come into the tank to scoop it out (possibly also hitting a fish with the net causing injury) can cause disease to attack the weakened fish and the subsequent deaths.

Try to mitigate temperature swings so that they are not so extreme and don't feed your fish if the water is cool enough that they are not eating.  As the water warms back up, be careful not to over feed as spring time is a common time for disease outbreaks when the fish seem to be eating well so the farmer over feeds and too much uneaten feed or water quality spikes can cause disease outbreaks during the warming weather of spring.  Columnaris disease tends to strike during the spring before the water gets back up to 80 F because it can grow rampant in uneaten feed and water quality spikes can leave the fish vulnerable to disease.

[Casey Haas]

I purchased my channel catfish from a reputable local aquarium store for an outdoor IBC tank which I initially had no intention of heating.

When I told the store owner this he told me that the catfish could survive the low temperatures but that I should NOT feed them when the water temperature went below about 55 degrees. He said that because they are cold-blooded, their metabolisms slow to a complete stop at such low temperatures and that any food that they might eat actually sits and rots in their guts causing them to be sick, or bloated, or even die. This made sense to me and I subsequently decided to heat my tank through the winter (for this reason and also to avoid killing the bacteria), and I haven't had any problems so far (knock on wood).

This may be the problem you are having you are having with your fish. Good luck!

[TCLynx]

Yep, if you are not heating the tank, you have to let the fish be dormant when the water is too cool (like below about 55 F) and what Casey says makes sense about any feed that is in the fish when their metabolism slows down too much to digest it could really mess the poor fish up so if the water temp is swinging up warm enough during the day for the fish to eat but then dropping too cold at night before they digest the food.....  that could explain dead or sick and dieing fish in the fall/winter.

In the spring as things start warming up, do be careful of the disease outbreaks especially while the water is between about 65-79 F since that is when the fish will seem to be very hungry but your bacteria might not be keeping up with the water quality and an ammonia spike can really irritate the skin leaving the fish particularly prone to the disease outbreaks of Columnaris, which is particularly hideous to experience.

[Dan Ponton]

So what is a good temp for fish and bacteria

My DWC is attached to an IBC which has Gold Fish.... I would not heat that tank.

[Casey Haas]

I chose to heat my tank to 66 degrees based on temperature numbers I took from Sylvia's book. I was going for a temperature at which to keep the fish eating and keep the bacteria growing and processing waste. According to the book, the bacterial growth rate decreases by half at 64 degrees, and goldfish and channel cats, which I have in my tank, apparently do fine in the 60-70 degree range, hence the 66 degrees. It is working out for me so far. There is probably a range of temperatures that would work in different situations though and you will probably have to take into consideration your goals and your system specifics in order to choose what will work best for you. Obviously you are getting by without heating so it isn't necessary for your system. I would just hold off on the food when its cold and be careful in the spring as TC suggested. Good luck!

[TCLynx]

Casey is right on.

Provided you can keep the day/night temperature swings the best temperature really depends on your goals and desires for the system.  If you can insulate things to the point that the normal day/night temp swing is about 10 degrees or less F, then if you are ok with minimal production through winter, you could let the temp stay low and just let things kinda hibernate while the temp is below about 55 F and then be careful about checking water quality and bringing up feeding slowly as the temperatures increase above 55 F in spring.

If you want to make sure you don't have to stop feeding completely (but just keep things ticking over at a minimal level) then having a temperature that doesn't drop below 55 F would be ideal.

If you want to make sure your system keeps going at a nice level through winter then you might want to pick a higher temperature for the heater like Casey does.