Does an Ro/di remove nitrates?

[JMLewis]

Just wondering. I just finished cycling my tank a couple weeks ago, so to bring down my nitrates I did 2 30g water changes 2 days in a row. So a total of 120g in 2 days and the nitrates were still through the roof.

So I decided to test my freshly mixed water and the nitrates were high in there too... So now either the cheapie trash can I'm using is leaching nitrates, my salt mix (instant ocean), or my Ro/di water has nitrates not being taken out by the filtration.

I don't have a freshwater nitrate test so I can't test my ro/di water currently. I bought a Rubbermaid trash can tonight so I'm gonna set that up as my new mixing container and ill test it after the first batch. I mainly want to know if I can eliminate my RO water or not.

 

[bsilvest]

I would say test that Ro water how long have your Ro membranes been running an also you are storing them when not in use wet or running a top off system an checking. Also are you testing your TDS of your RO before use, I also run my own OR and there is alot you have to watch just in that

 

[JMLewis]

Yea I'd have to pick up a fw nitrate test kit. I used my Salifert one and it showed nothing in my water for top off but I'm not sure if it only works for salt water.

My ro/di is set using a solenoid controlled by a timer that goes to a float valve in my top off container. It fills up the container twice a week. The its a fairly new 5 stage unit from BRS only about 4 months old and all the cartridges are original. I've changes out the Color changing DI resin twice so far. The unit has a built in TDS meter one for the water coming into the last chamber (DI resin) and one coming out. The one coming in usually reads around 10-15 TDS after it runs for a minute or so and the probe bor the water coming out of the DI chamber is always at 0. I'm sure I need to change the sediment carbon soon.

 

[JMLewis]

Still looking for an answer.

 

[Dr. Reef]

a regular RO membrane wont remove nitrates or phos effeciently but a HI-S membrane should remove about 90% of nitrates and the rest DI should be able to remove .

 

[JMLewis]

a regular RO membrane wont remove nitrates or phos effeciently but a HI-S membrane should remove about 90% of nitrates and the rest DI should be able to remove .

Would I just replace my ro membrane with this or should this be added onto it?

Also what's the difference between this and the ro membrane I have now?

 

[Dr. Reef]

TFC (Thin Film Composite) membranes will remove 95% of nitrates, up to 95% of silicates and is excellent for TDS (Total Dissolved Solids) removal. Hi-F (High Flow) membranes have the same characteristics as the TFC membrane but provide higher GPD (Gallon Per Day) water production. Hi-S (High Silicate) membranes are the gold standard and will remove 96% of nitrates and up to up to 99.5% of silicate. Chlorine will ruin TFC, Hi-F, and Hi-S membranes so prior carbon filtration is required.

 

[JMLewis]

Great answer thanks

 

[JMLewis]

Well mystery solved!! Last night I cleaned and hooked up a new Brute Trash Can as my new mixing container. Added salt and tested just now. Zero nitrates!!

The only bummer is that I never thought to test my freshly mixed water for nitrates before and I started using the old cheapie trash can (Mighty Tough 32g) 8 months ago. Since then I had uncontrollable bubble algae, slow degeneration of all my corals, which eventually led to a complete tear down and rebuild. I was doing tons of water changes to try to help before the tear down and now I realize I was probably hurting the tank more than I helped...

If I hadn't started new I might not have ever noticed it.

O well lesson learned ill be checking my new water for nitrates at least every other wc.