Hey, can anyone help. I have a common goldfish in a filtered 18l tank. The fish has came down with what I've read is fin rot. I've been to my local pets at home store on numerous occasions they have checked my water. I've given 3weeks of metaflix which reduced the redness in his tail, tried salt with water changes 30% every 3-7 days Now I've been given plimafix to try and well this has made the fish worse and the other fins are getting affected now. Please help dedperate mum trying rescue him for my little girl!