DI only vs RO DI


Premium Member
I have been thinking about
RO -DI water.

I am wondering why everyone runs Ro and di with the smaller tanks wouldn't it be more convenient to just use DI ?

Other than using up DI resin what are disadvantages?

I remember reading or being told that because of the ion exchange some kind of ionic imbalance could be achieved. This was never explained to me in enough detail to understand.

I have been using DI only water on my freshwater planted aquarium with good results so far.

I run pre-filter - 5 micron carbon block - anion bed - cation bed - mixed bed

My DI unit is not permanently installed.

Some advantages I see are

1 no waste water

2 water nearly on demand no waiting for hours while the Ro puts out product.

Looking forward to seeing what everyone has to say.


New member
The main issue you have is that DI does not remove dissolved solids. DI has not physical filtering.
So yes DI will do most of the heavy lifting, but you are still leaving some potential contaminants in the water including chlorides and dissolved organic matter (Which can break down into phosphate and nitrates).


New member
Also think that expense would be an issue. Depending on the TDS of your starting water your going to burn through DI like there's no tomorrow.

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Premium Member
I really appreciate the input.

I have been using DI water on my Planted tank successfully and it has not been that expensive

I've only exhausted one canister of DI resin $15 making well over 100 gallons of 0DI water I am Running a 1 micron fliter followed by a 1 micron carbon block followed by Cation resin followed by anion resin finally through a mixed bed. I am monitoring Tds between every stage. I know its not cheap but it beats buying water at the pet shop and having to deal with waiting for water and waste water and floods etc... 15$ DI refills are about the cheapest thing I've encountered.

I am listening when you speak of dissolved organics and other possible lingering contaminates. I certainly believe starting with perfect water is very important.

Thank you!