Back to the OP's tank--How about 6-8 corys (either species), 8 pygmaeus corys (a dwarf species that often swims low to mid-water level) & a pearl gourami. Skip the raph., pretty as they are, they are nocturnal, kinda big for the tank but with fairly small mouths (might be able to eat pygmy corys but not adult tetras or big corys). OR if you really want as many corys as possible (lol, love them!), you could think about habrosus, another dwarf & pygmy, 12 of each would be fun. Another cat I've never kept, glass catfish (since you like see-through fish). They may limit you other midwater choices, they're pretty shy--maybe a honey gourami trio & skip the tetras (I'm not a fan of many tetras). Upside down cats are usually better in groups & even 3 would be a lot full grown, maybe without the tetras & pygmys & 1 gourami, pearl for my preference. Will you have wood & plants?