I want to put uv light in a/c to stop mold, is that a bad Idea?

Are you sure that your tank smells of mold? Mold tends to develop in moist areas not in water itself. The scent you are smelling is likely a byproduct of the bacteria that the tank needs to keep the water safe for fish and other life forms to live in.

Also, if you have a filter that uses a cartridge DO NOT CHANGE THE CARTRIDGE unless absolutely necessary. Absolutely necessary means in simple terms that the cartridge has fallen apart. If it is coated in brown gunk, that is normal and you should remove water from your fishtank to rinse out the filter. Do not use tap water. If your tap water is relatively contaminate free you can use it to replace the water you removed after treating it with an agent intended to remove chlorine and chloramine I use Seachem Prime.

Remember, your fish tank should not smell the same as your tap water.

Please feel free to contact me with any additional questions you may have regarding the information I have provided.

/r/AskEngineers Thread