I use about a 1:10 bleach/water solution. I allow the tubs to soak for about 20 minutes, scrub them down with hot soapy water (just dishsoap basically) then rinse like mad under the tub facet with loads of clear, cold water rinsing. Then I wipe them with papertowels. With the glass tanks I'll also spritz them with a vinegar/water mix, wipe that off and air them out well until no smell remains so I can get the glass looking decent (I hate glass tank maintenance LOL).