How do I clean this?

[JamieTotten1996]

How do I clean this white stuff from the back of my tank? It’s really hard to get of, before I set the tank up I jet washed it, I scrubbed it, I used a knife and a razor and nothing worked!! So I gave up and set up regardless because I was told it’s harmless but now I’m curious if there was ever even a way to remove it?

 

[birdsnest]

Acid wash it with muriatic acid, citric acid, or vinegar and then scrape off with a razor blade.

 

[dwair]

Acid wash it with muriatic acid, citric acid, or vinegar and then scrape off with a razor blade.

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