Though its medical applications have declined with the advent of modern treatments, methylene blue still finds use today—in laboratories, aquariums (as a fish tank disinfectant), and niche ...

Some also buy it to prevent fungal disease in aquariums or for general lab use. Renue Blue is the first methylene blue formula on our list. It is designed as a topical serum—not an oral supplement.

Methylene blue is a synthetic dye and medication ... As per him, “The aquarium companies actually use it for fish tanks because it kills the mold off and cleans the water very efficiently.