Help! Accidentally used methylene blue based product. How to check safety of tank?

So I had a breakout of worms and mistakenly used a treatment that had methylene blue. As soon as I realized (only about 2 hours later) I took my one juvenile axie out and he has seemed 100% fine since (that was over 4 days ago so I am assuming I made it in time)

My question now is how do I assure the safety of the tank without entirely starting over? This is a 75 gallon tank so it would take an extremely long time to empty, refill, and then cycle.

My current plan is that I have been doing 50% water changes every day with my new siphon and that eventually after a week the concentration of the original treatment should be 0 or very very close to 0. My other concern however is that the tank has sand substrate. Is it possible that the methylene blue has become trapped in the sand and it will still be toxic? Is anyone aware of a way to test for the presence of methylene blue?

Thanks so much!

Dear Omgitsmogo,

I know this is hard but try not to worry too much. Methylene Blue is listed as a 'safe or relatively safe' treatment for axxies in low doses here: Axolotls - Health & Diseases

You can add Polyfilter to the tank if you'd like, which will absorb the Methylene Blue (it will change colour when it has done so), but Polyfilter is pricey (mine costs about £10 a block).

If you didn't use a lot, I wouldn't worry too much. Keep an eye on your axxie for the moment and observe him, but I should think you will be fine.