Posted: Sun Mar 17, 2019 10:52 am Re: Clean tank
I'm in a similar position. You can always try to contain the dirty water to the drain end of the tub, then rinse it with clean water, followed by a spray of a bathroom cleaner. Whether you use bleach-based products or ammonia-based products is up to you, I think both work fine. (obligatory NEVER MIX AMMONIA AND BLEACH)
I dump the majority of the water (as much as I can without dumping any poop or other stuff that settles to the bottom) into my shower drain, and then flush the junky water at the bottom down the toilet. I rinse and disinfect afterward.
If you haven't bought one already, get an aquarium siphon. They're easy to use and perfect for spot cleaning. My vet advised me to change 25% of the water each week, and 100% once a month. The siphon helps break the water removal down into smaller batches.