RO unit information for a reef tank

i run a 50gpd unit with DI resin in last chamber & an inline TDS meter is a must if ur gonna b in the hobby long..
very easy to hook up. usually just screws onto faucet or a saddle valvle and drain line goes to drain.I have mine in basement so it's outa the way. Bulk reef supply is a great place to get one & shipping is very fast when u need cartridge refills.

 

I would recommend the 75 gpd RO membrane along with a vertical DI cannister. I'm pretty sure the 75gpd membrane is the most efficient...and should be plenty for a 90gallon+ size tank.

In regards to hooking it up, it's pretty easy to install but depends on where you are installing it and what type of plumbing you have. I have PEX tubing and have fitting with a ball valve to turn off/on water. I would not recommend using the saddle-valve as once you puncture a hole in your pipe, it's permanent and prone to leak down the road...Plus they are not really intended to be used as a valve that gets turned on/off regularly.

If you are installing it near a sink, they have adapters that screw into your sinks water supply which is very easy to install and can ealy be taken off if you ever move.

 

I would also agree with the 75, I have a 125 and a 38 tanks and my 100gpd is great, does more than I need for top off and water changes. Another thing you should consider is a holding tank and a mixing container. I keep my RO water in a 55gallon drum and usually mix 20-30gallons of saltwater at a time.

Installing is easy, especially with the new plumbing hardware they have available, I just bought a 1/2" x 1/2" x 1/4" tee with a shut off at Menard's, cut the 1/2" supply line slid the push on tee on and was done.
I agree with Lee on not using a saddle valve, they are prone to getting clogged and they leak.

http://www.johnguest.com/Home/applications/beverages-and-drinks-dispense/Valves/Acetal-Stop-Valves/ACETAL-ANGLE-STOP-VALVE.aspx