New 20L Setup-Stocking Question

Small cichlid would work, but something like Rainbow or Keyhole (smallish and less aggressive). I had a small, yellow Leleupi and he ended up becoming hyper-aggressive toward my Cories yesterday, so I had to move him to my 15g (where he could rule all he wants as the Botia will sting his arse if need be).

Could get some Danios if all you're looking for is movement, or a knife fish...

What sort of setup do you want? You could easily add more tetras, as they will generally start to school with similar types of tetras. A school of 5 or more is always best. And a few more cories could be added as well.

I would add some more tetras of some sort and then maybe add a gourami (dwarf) as a center piece fish or a paradise or betta would be nice.

Maybe go with Rummynose tetra??...

My Serpea Tetra are very nice in color. Bright orange with black markings. The most entertaining fish in my tank are the Bloodfin Tetra, they are always up to something and learn new behaviour from newcomers. Ever since I got some Cories they scour the bottom of the tank for food, and with the arrival of two Ottos last weekend they are practicing a new swimming style, imitating them. Very fun to watch.

Also, I love my Ottos. I never considered them before, because they are so small, but they are very fun to watch. I traded in a larger sucker fish for the two. I really liked the sucker, but it drove me crazy how inactive he was. I was always paranoid about him, didn't know if he ate enough as he never sucked at the glass or anything else in the tank as far as I could see. Turns out he was nice and fat when I returned him, so he must have been eating, but it was just too much to worry about.

I would go with more tetras. there are tons of diffrent types you could pick from..here are a few of my faves

black skirt tetras
rummynose
cardinal
black neons
columbian tetras

scissor tail rasbora are also nice and stay quite small.

Emporer tetras are nice, so are silver tip tetras.

It would be nice if you could add some more tetras, preferably of the same type but do not have to be. You have a decent amount of room that could a number of community fish. Some smaller barbs, gouramis, platys, mollies, guppies, or danios should all do well.

I personally like platys because they are generally slower moving and will move throughout the tank. They should stay pretty small and can have beautiful bright colors. If I was you I think I would get 2 or 3 more redeye tetras and some platys. With 20 gallons I think you could easily have at least 5 platys as well.