I am thinking of maybe setting up a 5.5g instead of the 2.5g I was thinking of, only because of the selection of fish and plants I can put in it. I picked a nice piece of driftwood that takes up alot of room in the 2.5g which will probably look nice in the 5.5g tank...so here are the questions:

1. What plants with red coloration can I use? Something that doesn't get too tall for a 5.5g tank... I was thinking at least hairgrass, maybe brazillian microsword, glosso, riccia, and moss, but those are all green. I would like to add some red to the tank.

2. Fish selection and stocking. I don't want tetras, swordtails, or mollies. Don't want snails either. I would like to keep the tank about 75-80F. How about 2-3 otto and one species of fish? Will dwarf cichlids (like rams or something else) be okay? Or are there other fish that will be nice? I know I don't have much room to work with in a 5.5g so I don't expect to see schools of fish in the tank. I don't want tetras, mollies, guppies, or swordtails. I was thinking white cloud minnows, but want to see what other colorful options were available.

You're not gonna have too many options for such a small tank, which limits the type/amount of fish and plants that you can use in there.

As for a reddish color plant, there's really not any plant out there that will stay at that height for long. You're just gonna have to prune constantly to maintain them at the shorter height. Some red plants that comes to mind include R. indica and L. repens. They're relatively easy to maintain and their leaf structure works for the smaller tanks.

That's way too many fish that you're planning already. Otos will feel cramped in such small quarters and eventually they'll strip the tank of all its algae, leading to starvation. Instead, I would substitute the otos with shrimps instead. White clouds would indeed make a great addition. They're quite colorful, very hardy, and stay small. Other fish that you might want to consider are betta, danios, blue-eyes, and killifish (requires a tad more experience).

The fact that you're excluding tetras and guppies makes it hard, since there's so many great fish in those two groups. For tetras, there's the ubiquitous cardinal, neon (there's also a green neon) and jellybean. For guppies, there's always endler's livebearer or any of the other varieties.

BTW, no dwarf cichlids, especially rams in such a small tank.

Yeah, I dun think there will be any red plants that wouldn't need trimming in such a small tank. If you're ready for the challenge, how about some hardy rotala rotundifolia or ludwigia repens? Both would need strong lighting, Co2 and some kinda fertilizer though... also, the latter only has red on the bottom side of the leaves, but this can look really good!

L. repens has red on the entire leaf structure, on both sides.