u/ComfortableSystem545

hi, i’m a moderately new fish keeper who’s had only freshwater tanks and tropical things up until now, my stepsister recently moved out, and she left her a puffer and a tank full of shrimp that I do not know how to care for but I have been asked by my stepmom to keep the fish. It’s already has it set up, but I need to re-Aquascape it as it has not been taken care of. he needs a full tank clean, but before I do anything, I want to make sure that I don’t mess up his current cycled tank.
I’ve done a good number of Research on him and I know he needs low brackish water and a large amount of different types of food, including snails. I wanted to make sure that he is allowed to eat bladder snails (which I have an infestation of in my other tanks) and if the bladder snails need to be frozen or if he can eat them live. same with shrimp I have so many shrimp and I wanted to know if you could eat them straight up.
Some plant tips would be lovely. I don’t have any plants that are not freshwater and I don’t know if they would survive. Is there any plant I can put in low brackish water that’s recommended? He’s got SpongeBob decor that has to go. Thanks in advance!