Best way to get rid of hard water stains

If you clean it well afterwards...use CLR.

Straight white vinegar, not diluted.

I understand that CLR should not be put on the silicone. I hear that silicone absorbs the CLR and causes toxicity problems later for the tank inhabitants.

If it were me, I would set the tank on it's side and soak the calcium deposit in a puddle of undiluted white vinegar, then use a straight edge razor blade to scrape it off. If after all that the glass has etching, that means it was a freshwater tank that was left alone for months while the water evaporated, etching the glass as it dried up. 

White Vinegar is not harmful. A quick rinse afterward is all that is required.

Did you know that soaking in white vinegar dissolves those irritating Bristleworm bristles that got left in your hand/finger when picking up LR?

Aloha,
Mark


Edited by Mark Peterson - August 19 2013 at 3:39pm

Mark Peterson wrote: I understand that CLR should not be put on the silicone. I hear that silicone absorbs the CLR and causes toxicity problems later for the tank inhabitants.

I was not implying that the tank should be soaked in CLR. If you use a rag and apply the CLR directly to the hard water stains, wipe it off, and rinse, there should be no future issues.

I have used CLR with no deleterious effects. As with all products, it can be misused. As long as the clr is applied to a rag on the glass only and rinsed properly, there should not be any issues. It is up to the OP as to what risk he is willing to accept. If the tank is so bad that he can't see through it and vinegar hasnt worked, he may be willing to try something else rather than to trash it. CLR has removed stains that straight vinegar couldn't remove for me.

Well I tried clr today and it didn't work I have been reading online and they say toothpaste can remove light scratches so would it take off the etching too ?

Cerium oxide and a buffer...