Most tetras and rasboras stay small enough to keep in a 10 gal. Neons, ink spot rasboras, sepra, emperior terras are all good and pretty mellow.

Perhaps your platy is nuts from the ammonia poisoning durring the cycle. Just kidding. James has great suggestions. I like fancy guppy's. Maybe just dump that platy back to where you got it and ask for replacement, or just to take it off your hands. That way if you still want platy's you can get a small group of more peaceful ones. I think a large group of guppy's is awesome. They are small and don't add much to the bio-load. Oto cats, when they mature, don't show themselves much durring light hours. But they are great tank cleaners. Every tank I have had has at least a team of 5 as a cleaning crew. Once in a while if you can find zebra otos, they are real cool looking.

I was thinking about guppy's, since I've seen them at the fish store. We have three oto cats and they are always swimming around, kind of fluttering around, on the bottom and sides of the tank. That's disappointing to hear that they may hide during the day. My kids love the otos and the corys and have them all named and can actually tell them all apart!
I have heard that tetras are very hard to keep and die very easily. Of course I don't remember where I heard that at but it is what was keeping me from considering them. I see lots of mollys in the fish store. What's their story? They are kinda big though, the ones I've seen.
I've never heard of rasboras, sepra or terras. I'll have to look for them next time.

Perhaps you can take the Platy back to the petshop and get something else? I used to have a tank full of livebearers (Platys, Mollys, Swordtails, and Guppys) and another for Bubblenest Builders and another for.... Anyways, maybe you can another tank?

Good to know I can mix platys, mollys, swordtails, & guppys. I guess the platy I got is just a mean one.

Getting this tank started was a nightmare. It was my 9yo son's christmas present (please noone ever do this to a mom without asking first!) and of course he's not old enough to take care of it. i didn't ask for it, but i'm learning and i love watching them. but one tank is plenty for me!

Don't worry once you figure it out and this becomes 2nd nature and the tank is stocked to capacity you will have nothing to do but maintainance. then you may go back to the pet store to get new food or a filter or something. You happen to notice an awesome fish or 3 that you may want and you decide one day to upgrade because the 10 gallon which seemed so big and sufficient looks like a tea cup. Then you upgrade and the addiction begins. Enjoy it.

My dad started me off with a 10 gallon tank when I was 7. By the time I was in high school I had 8 tanks in our basement.