Hey Joel here's a list things you may need/want depending on your set up.
If you will have two large tanks you would want two Uniseal flexible adapters to tie the two tanks together. The tank you run the water into should have a float valve.
I also use the RO for the home drinking water, so I have a Y splitter on the output that allows for water to run to the large storage tanks and the small RO drinking water storage tank. Then I use a solenoid on a smart strip so that I can control when the unit is sending water to which tanks. It gets a little complicated as you can't really use the home RO at the same time as you are filling the tanks.
In my set up I keep a pump in one of the tanks to pump water up to the tank. But make sure you use a pump that is designed for ponds and is safe for fish and plants.
Do NOT use a utility pump!. Those motors are encased in a toxic oil that can wipe out everything that's alive in a tank if they leak. Ask me how I know.
The sizing of the pump is important. Much depends how high you are lifting the water. In my case I am pumping up from a basement to the first floor which is about 15 feet to where it comes out into the tank. So I need a pump with a good amount of head lift. For reference here is the one I use...
Pond Pump
I have an air stone and circulation pumps inside my storage tanks. They are controlled by the smart strip and are both run for four hours twice a day. But honestly just an air stone would probably be just fine too.
I used to run heaters but don't anymore. My tanks are in a basement storage room and the coldest they get is about 60 degrees. Since I run my tank in the low 70's that isn't that much of a differential and the fish and plants don't mind the drop at all (I don't run any heaters in the tank either).
Some options for the RO system which are nice to have are a pressure gauge and an inline TDS meter.
I hope that helps!