Cleaning Acrylic

[nmprisons]

So, my acrylic tank is starting to get some hard to clean spots on it. I have a mag float for acrylic, but it doesn't get this stuff off (seems to be some sort of calcium based algae - probably coraline - that is starting to grow on the glass). What can I use to get it off that won't scratch the tank?

Thanks

[raddogz]

If this is for the 25g tank then this should be relative easy.

Kent Marine makes scrapers for acrylic tanks...or.. you can use an old atm or credit card.

[nmprisons]

I was thinking about using a credit card, but was worried that it would scratch ... I wish I had a piece of acrylic to test on.