OK we've beaten this horse dead. Onto your questions about your 30 gallon
Stocking a 30 gallon can be very challenging and fun because with its size, there are so many combinations you can have. It sounds like you want more fish vs 1 or 2 larger ones.
First I'll start with the bottom of the tank...........
8 Cories will work well here. 30 is long enough to give them ample swimming room and they will help keep the bottom clean of excess foods. Also a very fun fish to watch as they are active almost all the time. There are many species of cories.
For the mid to top layer another small school of fish will work out nicely. You could go with most danios or tetras (neon, cardinal, bloodfin, black skirt, headlight/taillight,blind cave....the choices are almost endless)
You could still put in a pair of fish that get no more than 3 inches (such as a pair of gourami or similiar.
You could also still add 4-5 otos to the tank with no problems.
Rainbowfish are another alternative but your school will probably be smaller as they get a bit larger than tetras.
Just a few ideas. Others will chime in with more. Fish Doc is really good at stocking.