RO or DI?

When I goto the local organic grocery store to fill up on fresh water for top offs, I usually get Reverse Osmosis, but I see everyone's using RODI. Was just wondering - should I be using Deionized water or Reverse Osmosis or should I go 50/50 per 5gal?

Thanks!

 

ideally.... both. not just 50/50 but water that has been through both methods of filtration.

 

When referring to ro/di it is water that has been passed through a system where the water permeates a ro membrane and then has any remaining disolved solids removed via di resign. Aka what snooknredz said.

 

Well it pretty much gives me the option for one or the other. I can mix but either I fill up using RO or I fill up using DI :-/

If I wasn't living in a temporary apartment I would've already picked up my own RODI unit

 

Using RO means that most likely you will still have a TDS of 4-8 ppm. (thats what my ro runs). I am not sure what DI TDS runs but I am sure it is still above 0 so mixing the two will not yield you any better readings. I am sure someone else will be able to provide more information. I would try to get a TDS reading from the RO and the DI and see which is lower and use that unless you have access to true RO/DI water which has a TDS of 0.

 

you can easily hook up an RO/DI to a faucet (it is easily unhooked too so it can be stored away when not in use), in fact my RO/DI from Bulk Reef Supply came with the needed parts to hook up this way.

Mixing the two that are bought at the store will not do it for you. At the very least I would recommed buying a hand held TDS meter so you can test the water you are purchasing. You may be surprised by what you find. And at least then, you will know for sure what you are putting in the tank.

It's kind of like dosing chemicals, you would never put anything in that you weren't testing for (or at least you shouldn't ), so you shouldn't put any water in that you haven't tested either! You never know what harm you sould be doing if you don't test.

I hope that helps,

Jake

 

Funny thing is I purchased 10g of SW yesterday for a WC and I tested the salinity which read at about 1.020 :-/ He usually runs around 1.023 and I run around 1.025-1.026. So I wasn't pleased nor surprised that even LFS can't get it right. (not to mention his new employee sold me FW as SW one time and I was super lucky to have checked before pouring it into my tank >.<)

Not sure where I can find a TDS meter, but in reality I feel like the DI water would be more void of any substances versus the RO water, I just know that you don't want DI water for freshwater tanks because it's basically "empty." So I'm not sure if this applies for SW but anyway, I definitely should invest in a tap water RODI filter unit. Would save me monthly expenses in a very short time

 

You can find TDS meters all over online, I know for sure that Bulk Reef Supply has them, and any place that sells RO/DI units should sell em. With salt water, you want "empty" or pure water. Everything you need is in the salt mix, so you start with pure water.

When I first started I found the same thing with SW from the LFS, makes it hard for those starting out for sure.

 

A well maintained DI machine will be better than RO only. RO acts as pretreatment for DI and removes 90 to 98% of the contaminants so the DI lasts longer and works better.

You can't really put a TDS number to RO only except to say it should be about 98% less than the tap water TDS was to begin with. Without knowing the tap TDS number its only a guess. A good RO membrane is capable of 96-98% rejection rate or removal efficiency. On the other hand DI resin by itself is not 100% effective either, many contaminants are only weakly ionized so not easily removed by the anion and cation resins. A few of these include silicates, nitrates and phosphates, all of which may not be good for your reef.

Either way, a $20-$25 handheld TDS meter would be a good investment to make sure you are getting what you think you are. Something like a HM Digital TDS-3 or TDS-4TM is a good choice of meters.

 

+1 you guys thanks a lot for the good info!