Hi, My friend's fish got obvious parasites (scratching, flashing, and I'm 99% sure I saw 1 white dot inside a gill). I said get PraziPro. Prazi helped for like 1 day, but now the fish is back to scratching A LOT. What should I recommend? Edit: this is a goldfish and I think the tank & parameters are fine. Not my fish, not my tank so IDK. I think it's fine though. It's a 55 with 5 goldfish. Not ideal, but could be worse so I don't want to go the bet-a-bigger-tank route. He says it tests 0,0,5.