I have had this in some of my aquariums as well, I found the edge of a plasic card works best to scrape it off without scratching the glass. Its a pain but it can be done.

Sierra, good idea!

Seems like this is more bonded its almost like a white fog. I might have to drain it and really clean it but i just got my tank going perfectly.

The plastic card might work. It would be easy enough to find out, but if not, before you drain it after all that effort to get it going, try a razor blade.

If a window scraper with a new utility blade doesn't do the job, sad to say, you may have to drain it.

But now you know you apparently have something in your water that clouds the glass, so you may want to consider filtering it before you use it in your tank.

I suggest the plastic card because I am talking from experience. Razor blades with scratch the glass as will a window scraper or any kind of blade. You won't have to drain the tank....just do small bits at a time. Its a real pain, but it can be cleaned without damage to your aquarium.

Ah, sierra. Finesse. Never rush that type of job. If the blade is laid against the glass at just the right angle, it won't scratch it.

Not too much pressure, not too little.

Learned that from a pro. painter, who taught me the pro. way to paint all those little mullions, then clean the glass and leave a perfect edge, without scratching it.

The key, is a new blade and not using it after it's lost it's new, super keen edge. The sharper the edge, the less resistance to it.

Of course, if someone isn't really sure of their ability to use such a potentially lethal tool, I agree; best avoid it.

There are scrapers that use the old type double edge razor blades for shaving. They are really thin and flexible and less likely to scratch (haven't scratched glass yet with one) They are replaceable and can be found in the "razor aisle" at the local discount dept. store. If you can get them ccheap enough always discard the used blades. When blades are exposed to water the edges deteriorate quickly as it dries. They also make a flexible plastic scraper for acrylic tanks but they don't work as well on glass.

Use kelly clamps (surgical procedure clamps) to hold your razor blade.