What to clean gas tank with?

For those considering Muratic Acid I will post the following.

Muriatic Acid is diluted Hydrochloric Acid. Wear gloves and eye protection during use. Have good ventilation, and dont mix with other chemicals or a poison gas could be produced. Don't use in an enclosed area. Make sure if you get on your skin you wash it off thoroughly and wash the area for some time. This stuff works well, but can cause serious eye, skin, and lung damage. Be careful.