How can you stop this funky orange mold from forming on your goldfish tank sides and contents?

Answer 1

The brown/orange discoloration is a type of algae. Algea is the result of over feeding and/or over lighting. If you put more food into the tank than the fish can eat in 2 minutes, you are over feeding. Over lighting can be from any direct lighting such as a light strip for the tank or indirect lighting such as room light, sunlight from window or anyother lighting source reaching the tank.

Depending on tank size, water temperature and chemistry you could add a pleco to the tank. Gold fish being coldwater fish and plecos being tropical, this pairing will work most of the time as long as a comfortable middle can be reached. Standard plecos or L1's are the more active algae eaters, though they will outgrow all but a larger aquarium in due time. Most pet stores will allow you to return the larger pleco in exchange for a smaller one of same type.

Answer 2

To prevent orange mold from forming in your goldfish tank, you can regularly clean the tank and its contents, maintain proper water parameters like pH and ammonia levels, ensure good water circulation and aeration, and avoid overfeeding your goldfish. You can also consider adding live plants or a UV sterilizer to help control algae growth and mold formation.