You mention both a fluffy white coat on the fish and brown patches or spots as well as the lazy-like behavior. The behavior is common to a sick fish and the clamped fins indicate stress or in this case illness. Two potential diseases come to mind and both should be treated in a similar fashion so the difference isn’t really important.

I’m not familiar with Gold Disease Safe and Interpet is terrible about not giving active ingredients to their medications, but I do know many people have reported good success using their products.

Look closely at your fish with a flashlight and see if you can see a gold to rust colored shine in the white coating. It can be hard to see on a goldfish, as they naturally have a shine very similar to the color you are looking for, but it would probably stand out as a little different and may be most noticable around the brown patches or on the gill plates. If you see this, them assume you have a disease called velvet in the tank. To aid in the treatment of velvet, keep the lights in the tank off and if possible cover the tank for the next few days so that less light can enter the tank. Beyond that, continue treating as the directions indicate on the package and keep the carbon out of the filter. If you see no improvement in the next few days, try treating the tank with copper. It should be available at most pet shops.

Best of luck to you and your fish and if I can help further feel free to email me.

MM
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