I got a 15g tank as a temporary hospital tank right now while I'm still on the hunt for a larger tank for them, the tank came with an Odessa Barb, I read they should be ok in brackish water, I added in a little aquarium salt (maybe less than a tablespoon). When I put the puffer in there last night, he just sank to the bottom and wouldn't move, he looked a lot worse than when he was in the pet carrier so I took him out and put him back in a gallon container overnight with 2-3 drops of prazipro in the water. He refused to eat last night and this morning still, bloodworms soaked in prazipro solution or even regular blood worms. I tried to use a fork to drop some in front of him he just stares at it but doesn't eat it, and sometimes swims away from it. Meanwhile the other 3 puffers in the other hospital tank 10g go crazy for bloodworms even soaked in prazipro solution. This morning, I just put him back in the 15 tank (only him and the odessa barb) and he's swimming around at least.
I checked the parameters in the tank - they are all at the lowest readings, and it was the same in the gallon container too.
Nitrite NO2 0 ppm
Nitrate (0-20) ppm
Ammonia - lowest reading (0-.25 ppm)
The water was a bit hard and ph 7.5.
I'm not sure what I should do with the aquariums, I'm still in the process of trying to find a home for them so now these are just "hospital tanks". If I try to convert a freshwater auqarium to a brackish aquarium will the bacteria in it die? I'm trying to find a saltwater aquarium because when I buy a setup freshwater tank then I don't know what to do with the fish that's in there. But saltwater ones are expensive to manage. I made a post on craigslist that I would give them free to a good home but I'm not really expecting to find someone, because I don't think there's many people that knows how to take care of them.
So I don't really know what to do
After swimming a few minutes he stopped swimming and just sits there in a corner of the tank. I am not sure if I should take him out or leave him there :/ When he was in the container this morning he was moving his fins but now in the big tank he is barely moving and is turning darker colors. Does he have a parasite or is he recovering from the wound? I am not even sure what medication I should be giving him or if he even has parasites.