Blue Tongues, Bold Claims, And The Fish Tank Chemical Taking Over Your TikTok Feed

Never have I ever seen RFK Jr do something and immediately wanted to get on the bandwagon. I am apparently in the minority. Because when the Health Secretary was photographed squirting fish tank cleaner into his water on a plane, the next logical step for swathes of devoted followers on the internet was to do exactly the same thing. Their morning smoothies turned blue, and they posted a blue tongue selfie to prove their commitment to the cause.

Methylene blue is, to be precise about this, an antifungal dye. It has been used since the 1890s, primarily in medical settings for very specific purposes, and in aquariums to treat fungal infections in fish. It is the thing you put in the tank when your goldfish is unwell. It is not, and this feels like something that should not need saying in the year of our Lord 2026, a cognitive enhancer you squirt into your Evian at 30,000 feet because a cabinet member did it first.

And yet. The blue tongue selfie has become a wellness flex. Fitness influencers with hundreds of thousands of followers are posting photographs of their azure mouths alongside claims that methylene blue boosts mitochondrial (the powerhouse of the cell!) function, fights brain inflammation, enhances memory, and may even protect against Alzheimer’s and Parkinson’s.

Ben Greenfield, is a fitness influencer with half a million Instagram followers, called it “one of my favourite nootropics.” He definitely did not just read one 2015 study and extrapolate wildly from it. The doctors have some thoughts about all of this, and the thoughts are not positive. But between the RFK Jr plane photograph and the doctors’ notes, an entire wellness economy has sprung up around a fish tank disinfectant, and it is turning people’s tongues blue in the name of biohacking, which is a sentence that would have been incomprehensible ten years ago and is now just roaming free on TikTok.