as for the dwarf puffs... i dont know how many you could have in there but check your LFS and local chain stores.. callin is easyer than driving (and if yer not there you cant get something else)
i agree completely ive had them before theyre great little fish however they will need a little salt in there but thats all theyre not really picky and they live a long time. but if not you could do a betta/african dwarf frog tank those are cool. you could also get little fiddler crabs theyre fun to have
how many glowfish could i get in there? im going to put one of those corys that only get 2" i dont think he will take up too much space because they like to hide and chill