# When do you need to use RO/DI water?



## Ed_ (Mar 26, 2015)

Old reefer here but new to freshwater. I'm converting my reef tank now. I have RO/DI hooked up now and ready to go. It's what I've always used in my reef tank. I think the answer to my question will depend on my supply water and what I want to keep; but I haven't tested it yet. At this point I'm planning to keep neon or cardinal tetras, ottos (soft, acidic water would be ideal) and some low to medium light plants. I know with RO/DI I'd probably need to use a product like RO Right, right?

What are the supply water conditions that would indicate needing filtered water? 

If you had RO/DI already installed and ready to go, would you use it or get rid of it and use tap water? 

I also have a Python kit so I'm set to go either way. The water changes would be much simpler using the Python instead of the RO/DI.

Share your thoughts, please!


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## Clayman (Jan 7, 2015)

Depends on the source water, and what you want. Most of the time tap is good for plants and fish. Some people want to make a specific hardness and ph. I would use tap to fill and for water changes and maybe use the Rodi for top offs.


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## BeardedCrow81 (Mar 6, 2015)

Exactly as cayman said.
Tap water contains minerals that plants could use.
I've never heard of planted tank with pure RO, only reef.

Ugh it reminds me of my reef days, i didn't have a RO system and bought jugs of RO water and lugged it up the stairs of my apartment every week. Not fun!


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## WestHaven (Jun 30, 2012)

Some people use straight RODI water and then add a buffering product so that their water is at a specific hardness and pH.


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## Ed_ (Mar 26, 2015)

Clayman said:


> I would use tap to fill and for water changes and maybe use the Rodi for top offs.


 Hmm. That's something I hadn't thought of yet. Good call. I've got an auto top-off system (old school Nurce siphon-feed) that sits in a 5.5gal reservoir beside the tank that would not work as well with tap water (any nutrients or phosphates would cause algae and stagnant water).


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## Diana (Jan 14, 2010)

Most important reason to use RO:
Toxins in the tap water that you do not want anywhere near your tank- 
Use RO and add minerals to suit the livestock. 

Also important:
If you want to keep and especially breed fish or shrimp that do not like high mineral levels. Most tap water problems are too-high GH and KH for breeding soft water fish. If the tap water is otherwise OK, then a blend of tap + RO can work. 

Another good reason:
Topping off a tank so the TDS does not climb, especially if you are not doing large, frequent water changes. 

Knowing the tap water parameters, and the preferences of the livestock is the place to start.


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## kep (Feb 3, 2015)

I use straight RO water in my tank and use Seachem Equilibrium to raise the GH and remineralize. My tap water is very hard and I don't like the idea of having who knows what in it and having to remove bad stuff before the fish can use it. I'd rather start clean and add what I want. 


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## Ed_ (Mar 26, 2015)

kep said:


> I use straight RO water in my tank and use Seachem Equilibrium to raise the GH and remineralize. My tap water is very hard and I don't like the idea of having who knows what in it and having to remove bad stuff before the fish can use it. I'd rather start clean and add what I want.
> 
> 
> Sent from my iPhone using Tapatalk


 That was the approach I was going to take initially. I'm pretty sure my water is very hard. The appeal of not have to use buckets, trash cans, heaters, pumps, power strips, extension cords, and thermometers for water changes was all very appealing to me, and frankly a welcome break after decades of reefkeeping.


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## Diana (Jan 14, 2010)

Test your tap water, or look up the report from your water company (if you are on a municipal system).


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## kep (Feb 3, 2015)

Ed_ said:


> That was the approach I was going to take initially. I'm pretty sure my water is very hard. The appeal of not have to use buckets, trash cans, heaters, pumps, power strips, extension cords, and thermometers for water changes was all very appealing to me, and frankly a welcome break after decades of reefkeeping.



It is a pain to change the water. I use 5g jugs that I get filled at a local water store, then dump each one into a 5g bucket with a pump in it. I'm looking into an at home RO unit to hopefully save me some time and trouble. That is the only downfall. It's not very cold here in SoCal so I just let the jugs get to room temp and I don't have to mess with heating it. 

Most people use tap water and don't have an issue. If you are on the fence I would just look at what kind of fish you want. Unless they are super specific and fickle they should adjust just fine to tap. 



Diana said:


> Test your tap water, or look up the report from your water company (if you are on a municipal system).



+1 If the hardness is acceptable to you than it will likely work just fine. It's up to your preference really. 


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## All4Fish (Jun 23, 2014)

I started a planted tank with hard city tap water (in Michigan) and had many issues trying to keep water parameters stable, especially pH. I thought fish would adapt, but I kept losing them. I think it had to do with my municipality adding chemicals on a random basis to keep pH high. Check your city water report and then do your own tests as your pipes can still affect your water (my son started a water testing company so I am up to speed on his knowledge!) I finally switched to RO and all is great as I can keep everything totally stable; I only add equilibrium and baking soda to keep GH and KH at 4. (Diana helped with this!) I keep a large trash can on casters next to my counter top RO unit with a small pump for water changes. Easier than hauling and storing the python I used for my previous salt tank. Good luck and keep us posted!


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## S4UCE (Feb 20, 2011)

Also coming from reefing here. One of the reasons for switching over to fresh is being able to just use straight tap for water changes. Tired of filling, heating, mixing, and pumping. My tap is 6.5-6.8 so I should be okay. Someday I'll go back when I have a dedicated fish room with mixing barrels, straight RO barrels, sump, drains, etc plumbed together.


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## nayr (Jan 18, 2014)

Here in colorado our water sources change throughout the year, we have a ton of reservoirs and they change the supply every few months.. It can be great at sometimes of the year and then suddenly be very acidic, basic or very hard without warning... Ive tested our tap water multiple times in the same month and watched it swing from one extreme to the other when we were in drought conditions.

It was negatively impacting my house plants and took me a while to figure out, since then Ive put a 55g drum in basement with a RO filter and top off system, house plants are doing great so I've been using it on my aquariums. I use Kent RO Right to treat it and have had much better results, happy plants, and happy fish with no random illness or deficiencies anymore.

Check out http://www.purewaterclub.com/ for some very affordable RO filtration systems..

I think its easier to have someone care-take my tanks when I am on vacation; I can set it up to survive fine w/out a water change and all they have to do is keep the tank topped off... and with just RO water they dont have to treat it and I am less worried about a half-dozen topoffs without a tank change in there somewhere. (its very dry here, i loose alot of water to evap)


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## fishhes (Oct 18, 2014)

If I had an RO/DI system I would certainly use it. I am considering buying a cheap unit myself becasue the Nitrates in my tap water are ridiculous. I live in Des Moines and the DMWW lab report list Nitrates at 10ppm. My API test kit reads over 40ppm. Either way, I find that I cannot lower the tank Nitrate levels without diluting with RO/DI. I haul 10 gallons home from the grocery store every few weeks. Currently, the city I live in is suing two up-river counties for the extreme Nitrates being release by the agricultural practices in the watershed.


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## Raul-7 (Oct 17, 2003)

I use RO/DI and just use a bag of dolomite/crushed coral in the sump to raise dGH/dKH.


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## talontsiawd (Oct 19, 2008)

I use RODI water off and on. I don't have the equipment, I buy it at the LFS. One big reason I started to use it is someone I trust suggested the simple fact that you basically take out any variables so if you have issues you cannot figure out, then switching to RODI water takes out the possibility of something you are not seeing. The bigger reason I continued to use it, as I didn't find that to make much of a difference, is simply the fact I had way better luck acclimating fish, using the same water that the store uses. Basically, you take out most of the acclimation as the water chemistry should be about the same. 

I find on a new setup, I start with tap water until I am ready to add fish. I do two substantial water changes and keep using RODI water while I am adding livestock. Then I start cutting back over to tap water. 

Given my tanks are in the 10-20 gallon range, 10 gallons of RODI water usually lasts me a week or more. On a bigger tank, not sure I would take that on. 

As most said, it really depends on your water source. I have yet to see any claim they have substantially better results in fish or plant keeping unless they had really poor quality water. However, as others have said, it makes more sense once you are trying to get into a specific PH level, are breeding things, or have costly fish in general.


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