RO filters, for the most part, all use the same style cartridges and are rather "universal" in nature. If you are looking at an RO filter you will need to estimate how many gallons per day you will require. They produce water at a slow rate and they do waste about 2/3 of the water, so if you produce 1 gallon of purified water you waste about 2 more gallons therefore consuming 3 gallons to make 1.
A stealth RO filter will waste less water if installed with the restrictor on the brine but it will also go through membranes more often.
Since the filter makes water slowly you will likely want a storage tank for your purified water. This will allow you to have enough water on hand to fill your system without waiting. Extra water is good, just in case you have a problem. There are multiple ways to go about a storage tank, the simplest is a 30 or 55 gallon plastic water drum elevated on cement blocks with a float valve (fill) and a 3/4" or 1" grommet, barbed elbow fitting and shut off valve. I set my drum up high enough that I can slide a 5 gallon bucket under the "spigot" and fill it up. You can also use a garden hose adapter if you wish.
A permeate booster pump is a good thing and if your water pressure is low you will want a booster pump as well. If buying a package deal on a system you really don't need the pressure tank but if you use a booster pump then you can use the tank on the input side to reduce short cycling of the booster pump, just put the check valve right after the pump.
" and I intend to grow shorter style plants, but am considering buying the second extension.
