What could I put in my fish tank? [I Have a Fish Tank]

Thanks for the response but sadly I can't as my fish tank is freshwater.@Pfuzylogic

@MightyLion
I just find out the freshest they can survive in is brackish water.

Yeah, they need larger tanks though I think. @Pfuzylogic

It's not that I don't like them it's that they keep getting sick with fish diseases in my tank and now the tank is infected so any new fish I put in the tank will get sick and die. Luckily the disease only affects fish which is why my snail and plants are the only survivors so in order for an animal to live in the tank and survive more than two weeks it'd have to be non-fish. @Silverwings

@MightyLion surely bleach in the water would kill anything that is killing your fish.

Yeah but it would kill all the live plants in there and the snail, unless I took them out but that would be too complicated so I'm thinking of adding either ghost shrimp or a dwarf African frog to the tank as it is now. But I want some other ideas to cause those frogs are picky eaters supposedly and the shrimp are meh, I don't know if they'll be entertaining.@Silverwings