Red tail catfish temporary downsize


Feeder Fish
Oct 3, 2015
Hello, i am new to this site so please let me know if im posting incorrectly.

I have a red tail catfish. And he typically stays in my 180 gallon fish tank alone. He is about 16 or 17 inches, and is very healthy.

However, two days ago, we had a very minor earthquake, that sent a crack straight through my tank. Fortunately, it didnt leak. But i obviously had to shut down the tank. As of right now.... i had to put him in my spare 55 gallon tank, that i kept him in until he was about 8 inches. The dimensions of this tank are 4 ft by 13 inches wide... and 18 inches tall. Therefore, he really barely even has the ability to comfortably turn around at the moment. I am probably going to have to keep him in this tank until i can buy another other tank in three weeks. That tank will be a 210 gallon.

My question to everyone is, what can i do to keep my rtc safe and healthy for the 2-3 weeks that he must stay in a 55 gallon?

And please dont waste your breath yelling at me about how a 210 gallon tank is big enough. The tank was 3.5 times longer than he was... and 6 times wider than he was. By the reccomendation of my trusted, professional source who works with monster fish for a living, he assured me the tank is fine. The pic is of him now in the 55.



MFK Member
Sep 25, 2010
What a great looking catfish. For a couple of weeks aslong as water quality is ok id say he would be fine but no matter who you know is telling you 210 gallons is going to be fine its not they need a much larger tank than that.


Gold Tier VIP
MFK Member
Dec 31, 2009
Naples, FL, USA
Welcome to MFK!

(1) You need to make sure that he doesn't spoil the water, that is, the ammonia and nitrite are maintained at zero ppm by a test tube liquid test, like API, not strips. If you transferred the filter from the 180 to 55 that should help tremendously.

(2) Large and frequent water changes.

(3) I'd probably not feed it at all until the new tank is cycled or feed it very, very sparingly, although he may (try to) eat that pleco there. That's a very large bio-load for a 55 gal.

(4) Make sure the water entering your filter is highly oxygenated so that the beneficial bacteria grow and perform at their best.

(5) A crack can be rather easily repaired by siliconing a glass pane over it. A 180 gal would make a nice sump.

(6) No one needs to yell. Can't we have a constructive, polite, and mutually beneficial exchange of opinions?

Your 16"-long catfish's body volume is, very crudely (just eye ball it), 10"x6"x6" = 360 cubic inches. The 1 gal per 1 cu inch rule of thumb -- -- says a minimum tank size should be 360 gal (and a water flow / turn over that should correspond with this water volume). This is for an instant dilution of the ammonia it breathes out of gills to occur at a bare adequacy. Otherwise, the fish lives in a self-produced ammonia cloud around it, even though the water tests may even show zero (the difference comes from the dynamic state being different from equilibrium state AFAIU). 360 gal is also needed for a minimum mobility and minimum comfort.

It's your pet and you do what you do but it sounds like your professional source might be missing or just is unfamiliar with one of the most basic rules of keeping monster fishes. Not preaching from a high horse - I've committed this blunder plenty times when I got lazy and didn't calculate these simple numbers. I've sickened and killed hundreds of fish because of my self-confidence and vain conceit.

(7) I'd suggest a 300 gal Rubbermade stock pond at a desperate minimum, or better yet 1000+ gal intex pool because your RTC will be 2'+, ~1000+ cu inches very soon (if not it is either a runt = poor genetics, or is stunted, or is underfed). These pools are quite inexpensive. The usual problem is the space, of course.

Much luck!