i wouldn't suggest using bleach, but if you do, make sure you dilute it very well and let the tank sit in the sun for a day or two after you clean with bleach to dry it all out completely and remove the bleach leftover. i'd just use warm water, a scrub brush/toothbrush, and vinegar with a razor blade if the water doesn't work. with vinegar, just rinse well and you'll be fine. make sure you test it for leaks, just to make sure.