I was looking at the glass tanks that the retailers near me sell. I've heard some people say that some of the 40+ gallon tanks are nearly impossible to lift, so I was wondering how someone was supposed to do the thorough wash-out without lifting the tank. I was told to use a bleach solution of one cap of bleach to a gallon (litre?) of water and wipe it down, and the bleach would dissipate as the water evaporated. I'm not entirely sure how that sounds :S.

Are there plexi-glass/light (safe) plastic tanks that don't weigh a ton? And what would be a good way of conserving heat in a glass tank? I understand that you should black out three of the four walls so would black cloth do well to conserve heat?

Thanks!