What would be some good pets that could be kept w/ freshwtr fish but are NOT fish?

ok so i have a nice 29 gallon tank and everything and i was wondering are there any water creatures(that DO NOT need a above water platform and r fully aquatic,surface for air is ok,)african dwarf frogs arent sold my fish/petstore due to salmonalea and i already have ghostshrimp... thanks and i hope this question is undertandable.