Planted Tank Guru
Join Date: Jun 2004
Location: Baton Rouge, LA
Regardless of whether it's dangerous, there is no better time than when you already have equipment out of the tank to give it a proper cleaning.
Save the Excel, IMO. It's expensive. Just soak it in water with a little bleach for a few minutes. Then scrub the outside with a sponge. Use a bottle brush on the insides if you have one (if not, consider getting one). Rinse well.
Plastic isn't porous, so it doesn't retain much bleach. Adding a little dechlorinator to your tank before installation will quickly mop up any remaining trace.