Hi everyone :-* I am new to this site, I just discovered it yesterday and I've learned a lot already from reading threads. I didn't see anyone posting about this tho, so I figured I'd ask. I have two tanks, one fairly new 10 gallon and an older 50 gallon. On my 50 gallon tank, around the rims, and on the back of the lighting unit, is all of this whitish yellow crusty stuff, that is very hard to clean/get rid of. I can see it starting to build up on my new 10 gallon tank, and I have no idea what it is! Is there a way to permanently get rid of it? Or is it something that I just have to deal with? In my bigger tank, its been there for quite some time and doesn't seem to be doing any harm, other than the fact that it's ugly. Thanks!