I've got a 5 gallon tank that is home to a male Betta (mellow personality,) and 2 days ago I added 3 glass catfish. I got the glass catfish specifically because they are reported to be reasonable tank-mates for less-aggressive Bettas, and so far it has worked fine.

The glass catfish seem to prefer the bottom corner opposite the pump outlet, that the pump outlet is pointed at; they just school within that current. They rarely move towards the surface of the water, even at feeding time. If a piece of food sinks and then drifts in their direction, they'll ignore it unless it practically hits them in the face. Then they'll lunge and swallow it faster than you can blink. This differs from behavior I've seen in Youtube videos, where they'll swim up for the food.

Presently, I'm feeding them fish-derived flakes, because I didn't know any better at the time. I intend to buy some frozen worms tomorrow, but I've read that flakes are at least OK for an occasional meal.

I'd like to know what, if anything, I can do to encourage them to get up to the top of the tank before Betty[*] eats all their food. I could possibly redirect the pump outlet to point closer to the surface of the water, but that will make the Betta's food sink faster.

[*] Child insisted we name him Betty... can't be helped.

  • Done. While I don't have any experience with these, I guess they're just not used to their food not moving (they obviously prefer living food?). In time they'll learn.
    – Mario
    Sep 29, 2015 at 5:42
  • @RyanV.Bissell are these tank bred/raised glass catfish, or are they from the wild?
    – rlb.usa
    Sep 30, 2015 at 19:07
  • @rlb.usa it is my understanding that nearly all glass catfish are captured wild. Sep 30, 2015 at 21:04

2 Answers 2


For those of you who are using this for reference (I know this was asked years ago), please do not put glass catfish in a 5 gallon. They need to be in a school of at least 5, get to roughly 4" long, and need at minimum a 40g tank. The taxonomy of these fish is relatively unclear, and fish shops tend to get them mixed up.

They also tend to hide for up to a week when they are new to a tank, or indefinitely if they are stressed (which they would be in a 5 gallon). After a few days you should start to see the more adventurous ones come out from one of the (hopefully) many hiding places you've provided for them. I didn't see my 7th glass catfish for a month when I first got them, but clearly, he was eating because I been counting 7 ever since a month after I added them.

That being said, glass catfish are omnivorous who prefer a heavily meaty diet. They also will pretty much ONLY hunt moving food. If you feed frozen (like I do), having some current in the tank really helps the catfish get their prey drive on. It's a fine balance between having a current and not letting the food get sucked up into the filter. I also have an air stone that helps to move the food around. They're not the easiest fish to feed, but when you get it right, it can be very rewarding to watch.

Right now, mine happily accept brine shrimp, bloodworms, and a vegetarian mix. I'm constantly looking to vary their diet. I feed two cubes to my community tank every other day. I also feed them in the dark so my female bettas and glow-light tetras don't gobble everything up. The catfish are nocturnal and have a better chance of successfully competing for food when they are fed at night.

I've heard that it's difficult to wean glass catfish onto flake food, and some aquarists have reported that they were never successful in doing so. At the minimum, freeze-dried food should be offered.

Hope this helps anyone who might be googling this question.


This problem eventually solved itself, I guess once they got hungry enough to chase down food. I also did redirect the pump outlet to point closer to the surface of the water, to entice the glass catfish to school nearer to it.

I'll refrain from accepting my own answer for now, in case someone shows up with a better (or more insightful) one.

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