sizing and necessity of a RO\DI system


New Member
I have an established 125 FOWLER tank that I'm now wondering could potentially need a RO\DI system.
I've never had one before and am unsure of what size (gallon) would be best, let alone if it's actually needed. I'm starting to get a brown algae bloom but otherwise have had no problems with it overall.
So here I am, looking for advice.


Well-Known Member
Yes it is important to use RODI water. Long term you’ll have a better, healthier tank. Size of the system doesn’t matter much only in how fast it makes the water.
My tank is 120 with a 40 gallon sump. I have a BRS 5 stage unit. It makes,according to specs, 70 gal per day. In reality mine does less. The pressure of the water going into it is a factor and mine is at the low end of the range. I also use the RO part for drinking water and for ice. I have a pressure tank under my sink and have it plumbed to a faucet and to my fridge. That water doesn’t go through the DI resin. You don’t want to drink DI water. It only goes through the DI resin when it goes to the tank.


Well-Known Member
The RO is always attached, when the water goes to the tank it also goes through the DI resin. My DI resin is in a separate canister that is isolated from the rest of the system. When it is used for drinking it doesn’t go through the DI resin.
I have the RO+DI plumbed directly to my ATO and my salt. mixing tank. It is controlled by float valves. This way the ATO is always full and after a water change my mixing tank automatically refills.


Well-Known Member
There are a couple ways.
You need a water source. And a drain line
You can set it up permanently in the kitchen, bathroom, or laundry room. With this set up you attach the input directly to the water line. They make adapters that allow you to attach it to the area where the water shut off is. You also need a place to drain the waste water. In a permanent system that would be attached directly to the drain, again there are adaptors available. You will need a ball valve to shut it off when you aren’t using it. You will want to have a piece of tubing long enough to go to whatever you mix salt water in. It can be a permanent connection or a tube you just hang in a container. If you have a dedicated laundry room it is nice to set it up permanently with a float valve to shut it off when the container is full. This prevents the inevitable floods that will happen when you forget it is on.
The other way is to connect it to a garden hose. Not the best way but it works when it isn’t freezing outside.


Well-Known Member
IMHO RO/DI water is only needed for a reef tank with delicate corals like sps types.

Definitely not needed for fowlr tanks.

my .02


Well-Known Member
I have to disagree. The contaminants build up with tap water. As water evaporates and we top off with tap water the contaminant levels increase. Even water changes don’t help reduce them because we are adding the same water with the same contaminants back.