Direct out of the tap (Centerville City Water) 310 PPM

Basic refrigerator drinking water filter 210 PPM

Brita drinking water filter 115 PPM

Basic RO system including the below 4     PPM

10 micron sediment filter

Carbon Block

Standard RO filter

RO/DI system including the below   1     PPM

10 micron sediment filter

carbon Block

Standard RO filter

Two DI canisters with new resin

So as you can see, the difference between my basic RO system and the RO/DI system is pretty negligible.  The main reason for getting everything out of our water is to prevent algae growth, as many cities have a number of things that work like fertilizer and plant food in the water.  But there are other things that are good to remove too (fluoride, chlorine, chlroramines, trace amounts of led, etc.) as none of these are good for coral growth.  At 4 PPM though, none of these things are going to be a problem.

So if you really want to go over the top to have perfect water get the RO/DI filter, but I would say there is a 99% chance you won't notice any difference in the quality and health of your reef if you are using an RO only unit.

You may ask, "why are there so many RODI units being recommended and sold?" Money, profit, and the ability to fool the uninformed hobbyist into thinking that is what a reef tank must have. Our reefs need minerals, in fact we add lots of minerals in the salt mix and the food. Proper biological filtration and coral growth use and break down those minerals and elements into stuff the tank can use. 

FYI, some hobbyists with really beautiful tanks use tap water with all it's minerals. I personally don't recommend it because of the risk of contaminating the water with some accidental impurity released into the city water lines during treatment and during water line breaks/repairs.

Again, I suggest finding an RO unit locally here or on ksl.com. Between the two, an economical unit comes up for sale almost weekly, often for as little as $50. 

The only parts that wear out on a used RO unit are the replaceable filters and membrane. We can judge the life of the filters by viewing them and by asking the seller how long they have been used for how much total water. The RO membrane is the main part of the unit. It typically lasts for 5 years or 5000 gals.

Also, a $15 hand held TDS (total dissolved solids) tester can quickly and easily determine how good the unit is purifying the water.

Hope this helps. Feel free to ask more questions. I'm always available to help a fellow hobbyist, even via text or phone call to 808-345-1049

Aloha,

Mark  

Back to the unit though, I have kind of been looking at this unit from spectrapure...dont know if it will suit my needs though.

http://spectrapure.com/RO-RODI/RODI-SYSTEMS/Refurbished-90-GPD-RODI-System

Thanks

I have bought RO units locally on ksl.com for pennies on the dollar. In doing so, I acquire extra parts that I combine to build new RO units. I can build and sell them for less than $100 making a modest profit for my effort. Feel free to ask me how to DIY. It's really quite simple.

Aloha,

Mark  

808-345-1049