i would never use bleach on my tank, i alway use just plain water and a scraper to clean my tank it works just fine
I, as well as many aquarists, have been using bleach safely for many years, this topic may be of interest;
http
/www.fishforums.net/index.php?showtopic=119809&hl=
Start with the vinegar, and a plastic pot scrubber. If that doesn't work, CLR is the next step.
For really nasty tanks, Sno-Bowl toilet bowl cleaner is about as strong a cleaner as you can get.
*****Disclaimer*****
This stuff is strong hydrochloric acid. Use only in a well ventilated area, with safety goggles, long sleeves, and heavy rubber gloves. It will remove skin. It will give off fumes that will seriously irritate your lungs.
I use it outdoors, squirt it on, rub it in, and let it sit for about 5 minutes. Rinse realy well with a hose, double up on dechlorinator when filling. Go easy around the seams, it will soften them. I have used this on several tanks.
Sometimes the lime buildup will actually etch the glass given enough time, if this is the case it is permanent. This is usually seen on the inside, when you fill past the etched part it fades quite a bit.