Newspaper would be easiest and cleanest. Why 3 days for drying? Is the tank you are cleaning glass or plastic?

1:10 is a good ratio I use it and a regular (non scratchy) sponge on the tupperware to clean with. A thorough series of rinses coupled with good swabbing with a second (non bleach-infused) sponge


(EDIT - typing today is extra craptastic sorry)