The use of methylene blue in aquariums with shrimp is a topic of debate among shrimp keepers. While some sources suggest that methylene blue can be harmful to shrimp, others claim that it can be used safely at low doses and for short periods of time. Methylene blue may mess with the biological balance in the tank, and shrimp are extremely sensitive, so even if fish do fine, shrimp may actually die one by one.