If you get that white crusty line or lines in your tank, and haven’t found out how to get rid of it, or didn’t think it was possible, I have one word for you: Vinegar
I spent several hours completely cleaning my fishtank today, and found that using vinegar removes these calcium deposits. In order to do this, completely remove everything out of your fishtank, fish, plants, gravel, EVERYTHING! Soak it in vinegar. If the calcium is near the frame or near the top, soak a paper towel in vinegar and place it over the area. Leave it for a couple of hours, then rub and scrub it off easily. It got 98% off of my tank.
Make sure to thoroughy rinse your tank afterwards so that your fish wont be affected.
then enjoy your sparkly clean tank :) 5 years ago

it needs some serious help 5 years ago