Black Moor Goldfish dying....

Question
My tank has been set up for several weeks. I have other fish breeds in my tank currently that are not dying but it seems that every time I put a Black Moor Goldfish in the tank it dies. (They are just mollies) None of the other fish are being affected by this disease. My Black Moors have a red rash under their chin, they loose their scales, they look like their scales have been through a shredder and there seems to be a white filmy/moldy-like substance on their bodies. I change all of my tanks with pure water and do tester strips on a regular basis. All of the levels are in normal ranges. Please tell me what I am doing wrong. Thank you.

Answer
Hi Svenja;

Goldfish are coldwater fish so it may be the higher tropical temperatures that weaken them and cause eventual death. The symptoms on their skin and scales indicates they may be getting nipped and bullied by the mollies too. It's all just too much for them. Goldfish have a much thicker slime-coat than other fish do and others are often attracted to it. The mollies may simply enjoy eating it and the moors are not fast enough or agile enough to escape their tankmates. I know it sounds horrible but it happens. Goldfish are just better off in a coldwater species tank with other goldfish of similar size, speed and temperament.

At Your Service;
Chris Robbins