Large calcium deposits

[nooboftanks]

I was recently offered a 37gal bio cube with live rock and filter media so how could I not take it! Like most used tanks it needs some deep cleaning but I’m having some trouble with what the previous owner called “calcium deposits” they are a deep red color and I’ve tried everything including spraying them with vinegar to get them to go away

[Sniperhank]

Coraline algae. A calcium based algae that is a sign of a healthy tank. Pretty hard to get rid of once it gets a foothold. Lots of vinegar soaks and razor blades.

[coralbandit]

If you are going marine leave it...
If you have to have it gone soak vinegar wash cloths [paper towel ] and turn tank on side and let it soak into the coralline before trying to scrape.