IMO, the bleach/water solution should be more than adequate to clean the turtle tank out. No bacteria will survive the bleach. Just make sure, as mentioned before, that you rinse the tank VERY well. Instead of a sponge, I use an algae scrubber pad from the LFS. Costs a little more I know, but it's safe and it'll cut through gunk that a lot of soft sponges won't touch. Vinegar, although I doubt it would kill any parasites or bacteria, is very good for cleaning tanks also. It'll cut through hard water deposits. I use a vinegar/water solution to clean the outside of the glass on all the tanks I care for. If you have the white deposits on the inside of the glass after you clean the tank with bleach, fill it up with water and add a quart or so of white vinegar. Throw in a PH or small pump and let it percolate for a couple of days. All that stuff will wipe right off.