To add. I think it is nice to have/need to have to have a net. So you can scoop out dead fish, floating leaves, and catch fish to move them. I use my net all the time to skimm duckweed off my 55g.
Another useful thing I have, more in the nice to have, is a turkey baster just for fish use. It is useful for getting water out for testing, and is perfect for feeding frozen foods down to bottom feeders.
Also, if you don't have a python, you need a bucket that is just for fish use. If you use your mop bucket to fill your fish's tank, the soap will kill your fishes.