Basic fish tank supplies would be, well, aside from your normal filter, air pump, heater, lighting of the aquarium, supplies would be, you're going to want a good test kit. You're going to want to test the pH, your nitrogen cycle - namely your ammonia, nitrite, nitrate. It also doesn't hurt to test for phosphates. You should also have, if you have a reef aquarium, you should know to test for calcium, alkalinity, magnesium. You could also do potassium and iodine. Those are also very important.
You're going to want a good algae cleaner whether it's a sponge, whether it's handheld, on a stick, anything to get to the viewing panel of the aquarium. You're also going to want a good siphon. I don't like siphons that connect directly to the sink. It doesn't give you the control to add dechlorinators back to the aquarium when you refill the aquarium, and it also doesn't allow you to prefilter the water before it goes down your drain. A lot of times when you're siphoning water out of the aquarium by cleaning the gravel bed you have a tendency to suck up gravel or sand. You don't want any of that to go down your drain. So you're going to want a good siphon kit, a couple of five gallon buckets.
I also recommend when you do your water changes you get a plastic tarp. You can get them at Home Depot or Lowe's for just a couple of dollars, but it could save your floor. Remember, water and hardwood floors do not mix. Even if you soak it up right away, if you spill water on your floor it's going to immediately soak right into the floor, get into the cracks, and it could raise those panels resulting in ten to fifteen thousand dollars in floor damage. So put down a big plastic tarp, a drop cloth in front of that. Preparation is key. Get a couple of five gallon buckets, and be prepared to go at the tank for 30 to 45 minutes.
And then you're going to also want your pH control, like up and down, in case the pH is off. It's always going to either be a little bit too high or a little bit too low. You're just going to need to counteract the effects of acidification or the pH getting too high.
And that's it. Those are your basic pieces of equipment that you're going to need.