build up on aquarium glass

Question
I have a tank that has been set up for years.  I noticed lots of black algae begining to grow.  I asked at Petsmart employee what to do he suggested I put in these fizzy tablets to clear up the algae and some other fizzy tablets to clear up the "cloudy" water... it managed to kill several of my fish and didn't do anything to remove the black algae not to mention leaving a heavy milky film on my glass on the tank.  If I use an abrasive pad and LOTS of scrubbing... I can get it to come off the glass... is there a better or easier way to get this "film" off the glass?  It looks like it could be a calcium build up? The tank has NEVER had this problem before... what would cause this in such a short period of time and what can I do to clean it off?  Thanks for your help.  

Answer
Hi Christine;

The white buildup could be from all the chemicals that went in there, or could even be a little bit of the algae that was just barely beginning to grow there and was killed by the chemicals. In my tanks to scrape stubborn stuff off, I use a single-edge razor blade on the glass and CAREFULLY scrape it off. Avoid the sealant and especially avoid your fingers! I had some of that crazy white buildup on a plastic tank and couldn't use a razor scraper or it would scratch. I drained the water level really low and used a dry paper towel to gently scrub it off. It worked just fine with no harm to the plastic. I don't know what the stuff was.

Here is info about "brush algae" which is what I think you may be dealing with;

http://faq.thekrib.com/algae.html#brush

Good luck......

At Your Service;
Chris Robbins