I had bought 6 rummynose and the seemed to school. A week later I bought 4 more and now they don't seem to stay together anymore. Any thoughts on why? I do have 10 neon tetras, 3 albino cats and 4 small platys in the planted 29 gal tank.

Thanks for the welcomes. Glad to b a part of fish forum

A 29 is kind of smalll to get consistent schooling, and as jccaclimber says, if there is no reason to school, they'll spread out. They school defensively - it's fish convoy behavior.
In a 29, as soon as they get a groove as a school, they reach the glass. That breaks the group up, and after a few times, they may not reform.
I have a four foot tank with a magnificent school of African tetras, but really, they school when the cichlids that rule the bottom go into spawning mode and become mildly aggressive. That can be a hard game to play for us, as if the fish that triggers schooling is too aggressive, the school gets destroyed.
I just consider myself lucky that I stumbled on a balance.

I have a friend who's an underwater photographer, and I've looked at Amazon shots including lots of wild rummy noses. They usually appear in groups of a few dozen, but not all moving in the same direction or forming massed up schools. It didn't appear too far off what we see in the aquarium, on a different scale. The ones that are always in big schools are the cardinals.

I think all aquarium schoolers are pretty much the same.....once their numbers are more they break up into smaller groups. Saw similar behavior in my 125g when I went from 5 to 17 Rummies. They feel comfortable with a certain number and once it is reached, nothing to keep them all together. Exact same behavior out of my Blood Fins and they school much better.

I have about 60 Cards. They shoal maybe, but far from schooling.

Thanks for the feedback. I'd rather have the rummynose comfortable rather than have them school for defensive reasons. They are great fish and I love watching them.

I never said it got worse, but if a group of 6 or 7 feel comfortable enough to move around the tank as they please, adding 10-15 more won't change that. I had 5 and for the majority of the time they stayed in the plants, not really hiding but they didn't seem to move freely about the tank. When I added 12 more it changed it up. They will sometimes move all together, but there are a lot of times now that they also move around in smaller groups. Having big groups doesn't mean they will stay together all the time.

I have 10 rummy nose in 48" tank ... I notice the rummy nose like to school all together and they split up as well at times....watching them right now. For most part they school real well though. Maybe it is due to longer tank, first time I have owned them, beautiful fish.