Anyone using RO water for freshwater?

[hjsvt]

If you’ve seen some of my other posts, you know I have been dealing with water issues from the beginning. My problems continue but I’m making process and this is the latest. I hope there is someone experienced in using RO water in freshwater aquariums that can offer their support and advice.


To quickly summarize, my well water is very hard (23 GH, 20 KH) and our house supply of water is run through a softener. The pH of the well water seemed fine even after sitting out (~7.6). But the pH of my tank was increasing significantly in just a day or two after water changes and has gotten as high as 8.5. Originally I thought it was the result of ammonia dosing during my fishless cycle and wasn’t worried because everyone says when asked “stability is much more important than actual pH”. I purchased an RO to cut my well water (before softener) 1:1 and started doing water changes with mixed water. However, my pH was still climbing even after ammonia dosing ended. I purchased fish from my lfs on 3/8 and they advised me against purchasing a couple of things I wanted because of my pH. So I added a filter bag of peat granules to my tank and managed to maintain a pH of 8.2 for a couple of days and now 3 days later I’ve dropped a point in GH and my pH has dropped to 8.0. In the meantime, I have been running an experiment to determine what is causing the pH increase. I thought it might be the Flora-Max/Eco-Complete substrate mixture in my tank after researching and seeing other’s posts on the subject. So I set up a controlled test to determine if that was what was happening in my case. At the same time, I also did a test of the 1:1 water mixer with a bubbler added, something I hadn’t done before. Previously, I had only let the water sit in a bucket over several days with no agitation. A picture of my pH results from this morning is attached. The Flora-Max/Eco-Complete does increase the pH of control RO water. I saw the biggest change with fresh material straight out of the bag compared to the older material from my tank. This does make sense as there are no buffers in the 100% RO water. So if you are going to use this substrate with very soft water, I would be cautious. However, there was no significant difference between the control 1:1 water with and without the substrates. AND the control water pH increased over time with no agitation and nothing else added!! AND the pH of the 1:1 water with the bubbler agitation was even higher with a pH of 8.4. So I feel like I know what going on now, which is a huge relief! (What do you know; it all comes down to the H2O out of my well again!) So I feel like I have two options, 1. I can continue with the 1:1 water but I’ll need to premix and pre-agitated it prior to use for water changes to minimize the pH swings for my fish. I’ll also have to continue the peat additions which is not exact and is a slow process. This also means my tank pH may stabilize around 8 which is not bad but does limit my fish options. Option 2. I can run 100% RO water with additives to create exactly what I need. The cons are I will have to make more RO water and use chemical additives. The pros, I should be able to maintain a lower stable pH which increases my fish options. I think the time involved, water storage space and power usage are all about the same for either option and make them a wash. I’m leaning towards option 2 at the moment. I’m thinking I can minimize pH swings and stress on my fish by gradually shifting to 100% RO water by making all my PWC with 100% RO water slowing over several weeks. I’m thinking of 25-30% PWC weekly until I get to a stable lower pH.



So I’m wondering if there are other drawbacks to the RO water that I don’t know about? I have created a formula where I’m adding Seachem Alkaline and Acid Buffers, Replenish (but I’ve ordered some Equilibrium and will be switching to that), Prime, Phosphorus and Flourish Excel. Anything else I need to consider? Also, I made up about 3 gallons of this combination this morning and added it to a bucket with a bubbler to monitor it over a few days to see if in fact the 100% RO water pH remains stable with agitation. My final formula before agitation gave me a pH of 6.8-7.0, KH of 8, GH of 9, phosphate of 0.25-0.5. I hope you’ll share you RO water expertise and any thoughts you might have. Thank you.

Here are my test samples from left to right:
#1 - New Eco-Complete with 1:1 RO:Hard Well Water
#2 - New Eco-Complete with 100% RO Water
#3 - Flora-Max Substrate Mix from my tank with 1:1 RO:Hard Well Water
#4 - Flora-Max Substrate Mix from my tank with 100% RO Water
#5 - Control 1:1 RO:Hard Well Water (no substrate)
#6 - Control 100% RO Water (no substrate)
2nd from right - 84 hours 1:1 RO:Well with bubbler
last on right - tank pH today

 

[Andrew McFadden]

Many breeders use ro water for different things including myself. Just an FYI API GH/KH kits are horrible imo.

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[Fresh2o]

Andrew - Which kit would you recommend? I use the API kit so infrequently but curious about alternatives.


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[Andrew McFadden]

I never noticed till I went back to salt how far off the readings were. With saltwater I was recommended to do top of the line Salifert and it can be used on fresh too.

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[hjsvt]

Do you recommend the salifert test kits for ammonia, nitrite and nitrates too? Do they work with freshwater too? I don't see one for GH? I thought this was very important for fish respiration? It would be pretty expensive to switch everything over now.

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[hjsvt]

Also my first test 3 gallons was exactly where i expected it to be based on my calculations and buffer additions with my API test kits.

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[Andrew McFadden]

Api seemed fine on those kits. Salifert is a little easier to read and pinpoint. I'm only using my Salifert kit for my salt tank now. I'd have to look and make sure it says can be used on fresh cause I haven't used those parts of the kit for fresh.

If the Api is all you've used then you won't notice an issue. It will still go up and down if your changing it. But it's not what it really is. At least it wasn't for me. Personally I wouldn't worry about it especially if your going to use ro. Just make sure you always do everything the same so things don't spike or do a switch hitter on you

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[uncgirl1]

I'm sorry! I wish I could help. I have zero experience with RO water. Seems like there should be a way to stabilize your ph as well. It's unbelievable that your well water would be so unstable as far as ph goes. There's bound to be a solution. We just have to find it!


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[hjsvt]

Thanks uncgirl1! I'm working on it and feeling like I'm getting closer to a solution. Did you see the comment about the Salifert KH test? I ordered one today. I'm going to compare it with the API test kit and see what I think. Thought you might want to know about it too for accurate KH readings with low KH. I'll let you know what I think when I get it.

 

[uncgirl1]

Thanks uncgirl1! I'm working on it and feeling like I'm getting closer to a solution. Did you see the comment about the Salifert KH test? I ordered one today. I'm going to compare it with the API test kit and see what I think. Thought you might want to know about it too for accurate KH readings with low KH. I'll let you know what I think when I get it.

Yes, I saw that. I'm very interested to see what you find.


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[Eggheadfish]

Following. All of my tanks have a standing ph of 8...hard water and lots of dissolved CO2, it tests neutral from the tap. I was thinking about investing in an RO unit but I'm not well versed about any of it.

 

[uncgirl1]

Did you get the new test kit? How are things with your water?


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[hjsvt]

***UPDATE***

So while typing the response below I had some ideas I decided to try. I really wanted to know what the well water KH was with the Salifert kit. So I decided to make some RO:well water mixtures and test them with both kits.

1:1 RO:Well Water API - 8 Salifert 11.5-11.8 (so well water is probably at least 23-24)
5:1 RO:Well Water API - 3 Salifert 6.1
7:1 RO:Well Water API - 3 Salifert 5.1

So I've changed my mind, but I definitely need to continue to do more. The Salifert is more sensitve (maybe not more accurate?) So at lower KH number I wasn't seeing a change in API drops but I am seeing lower Salifert numbers. I definitely need to do more testing and see if this pattern continues.

I started another bucket test with the 7:1 water to see what happens with it over time.

Did you get the new test kit? How are things with your water?

Yes I did get it. I was away for the weekend again so today was the first time I've tried it out.

My first impression is the Salifert test is harder to use. It may be more accurate but that may be offset by increases in potential errors by increased test difficulty. However, by 4 trial tests and I seemed to get the hang of it. The titration liquid is added with a 1.0 ml syringe and I find it very difficult to control the amount added without a drop hanging off the end but not going in and getting too much at a time and potentially missing the color change point.

I have 3 ways to measure KH right now, strips, API and Salifert. So I tested straight RO water, an RO water mix I created with buffers added and my tank water today. As expected the strips are the least accurate and really don't compare to either test except with straight RO water when KH is zero tests do agree. What I found with the limited testing I did was the lower the KH the closer the API and Salifert test were. Again with straight RO water, 0 KH, all tests said zero. My buffered RO water had a API KH of 4 dKH and the Salifert said 5.4. My tank water had a API KH of 7 dKH also but the Salifert test was 9.6-9.9. So it appears that as KH increases the discrepancies in the test increase. But so far my data is limited. BUT it does makes sense with what I have seen going on with my water. So I leaning toward believing that this trend is accurate. So if you have a low KH, I think the API test is probably fine. If you are dealing with harder water and higher KH then the Salifert test may be a better choice but does the increase in potential errors offset that? I don't know. Another disadvantage for me with the Salifert test is it only goes to 15.7 dKH. My well water with the API test is 20+ and if the trend of the Salifert KH increasing exponentially was accurate (big if) my well water is off the charts. BUT this does correspond to what I seeing with my tests every time I add well water to the mix. It's almost like there is even more KH in there than I can test for and as I lower the pH it comes out from hiding and my KH goes right back up, along with the pH.

The good news is my fish are doing fine. I've been away two weekends in a row and I've had no losses and the automatic feeder appears to keep everybody happy without effecting water quality. The bad news is 2 hours after a 50% water change 4 days ago pH was 7.5 and KH was 7 (API), 4 days later pH is back to 8.2 and KH is 9 (API). My plants are not looking good. My nitrates were between 0-5 ppm this morning but after looking at some charts and photos this morning the deficiency appears to be iron. Also I'm having a brown algae outbreak. So I'm hoping I can get things back in balance over the next few days and my plants start to look better. Super glad my fish appear to be happy and can handle the water change pH swings!

 

[Andrew McFadden]

Couple other things that can be pointed out with the Api kits. If you took a look at your test vials where they are all lined up. Look at the 5 ml markings on each one, notice anything wrong?

Also how could you be sure that each drop of solution = a certain amount? That's why other brands have changed to actual syringes.

Anyways its nice to actually see someone take the time and try to figure this out on their own for the most part. It doesn't happen much anymore most people just take the words of others advice and not find the science behind it all.

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[hjsvt]

Couple other things that can be pointed out with the Api kits. If you took a look at your test vials where they are all lined up. Look at the 5 ml markings on each one, notice anything wrong?

I have definitely noticed this!! What a coincidence that you mention it! I have started measuring the liquid volume for the API test with a syringe or graduated cylinder.

Anyways its nice to actually see someone take the time and try to figure this out on their own for the most part. It doesn't happen much anymore most people just take the words of others advice and not find the science behind it all.

Thanks! I'm trying hard to figure my water chemistry issues out so I can make the best decision on which way to go. It's definitely a challenge. The latest thing I don't understand is why when I finally get a water mixture with a KH reading of 3-5 why is the pH still 8+? I was hoping if I got my KH down my pH would naturally come down too but that doesn't appear to be the case. It's like my well water has this massive amount of buffer in there that isn't KH and this mystery buffer is even more effective than KH in maintaining the high pH. But I have no idea if I'm even on the right track with that crazy statement. Frustration talking!

 

[Andrew McFadden]

When you make rodi water your ph does not automatically drop. It keeps it's ph level from my understanding. With all the stuff the filter removes you can easily change the ph by adding back what is needed. So if you have a substrate that is suppose to lower ph it will much easier now or by adding tannins. Or when you make the water and add it to the tank it should take on the same ph level that is in the tank.

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[Linwood]

I did much the same as you, starting with the mixture of acid and alkaline buffers, and equilibrium. Over time I found the acid buffer was doing more harm than good, it seemed to fade (for want of a better word) over time, and the ph/kh drifted higher.

I've had better luck just dropping that, and settling on whatever ph the kh ends up providing (in "normal" water there is a direct relationship between kh and ph). It's hard to get near 7 ph with a KH that high, just look at the co2 vs kh vs ph charts. Your mileage may vary of course, but at some level keeping ph high and kh low is likely to prove a bit of a challenge.

On a related note in terms of philosophy (and this is contrary to a lot of advice) -- I personally see no purpose in mixing RODI water with tap water, unless you are trying to save small amounts of money. The main reason for using RODI water for most people is to take control of their water chemistry, to not have to worry about whatever is in their tap water.

So if you are mixing RODI with (say) 50% tap water, what you are doing is taking only 50% control over your environment, but going through all the trouble of an RODI system to do so. For pennies more and a bit more run time, you get to take 100% control.

So why bother?

 

[hjsvt]

Thank you, thank you, thank you so much for taking the time to post! I feel so much better! This was exactly what I was hoping to find, confirmation that there are other "rebels" out there going "against the grain" so to speak.

I did much the same as you, starting with the mixture of acid and alkaline buffers, and equilibrium. Over time I found the acid buffer was doing more harm than good, it seemed to fade (for want of a better word) over time, and the ph/kh drifted higher.

I've had better luck just dropping that, and settling on whatever ph the kh ends up providing (in "normal" water there is a direct relationship between kh and ph).

That is really great to know. I suspected the same on the acid buffer but I've only been testing it a couple of weeks now and hadn't reached a definite conclusion. So glad to know you saw similar results. The higher the KH, the faster the acid buffer appears to lose it's effect IME. Right now I'm trying to determine the best combination for 50% PWC to achieve the final desired result in my tank and slowly remove the well water that is in there. I suppose I could do a 90% WC but I was trying to proceed slowly and carefully for the benefit of my fish and minimize pH swings as much as possible. Eventually when the tank is where I want it. I will have a different PWC mix to maintain the tank parameters. So it will be an on going process with lots of testing for the next month or two I'm guessing. Right now my tank has a Salifert KH of 10.2 and pH of 8.0-8.2 with a small bag of peat granules suspended by the filter outflow. I've been really happy I've been able to maintain that pH and I haven't seen any more climbs into the higher 8.4-8.8 pH ranges. I finally let some well water sit for days (I can't remember the # exactly it's at least 8 probably more like 10) I get a thin white precipitate on the top which I thought at first was dust but a similar bucket of RO water left in the same area for the same time does not have the same stuff floating on top. So I think something in the well water is coming out of solution as it reaches room temperature and floats on top of the water. Also the pH now of that bucket with the API Wide Range drops says 9.0. It may be higher. I ordered a pH meter today along with calibration and storage solutions.

It's hard to get near 7 ph with a KH that high, just look at the co2 vs kh vs ph charts. Your mileage may vary of course, but at some level keeping ph high and kh low is likely to prove a bit of a challenge.

Ideally I would like to get a stable tank at around 4-6 KH with hopefully a pH of 7.5. I'm not looking for a high pH and low KH. I'm really hoping as I lower the KH my pH comes down to a more reasonable number. In some tests I have going currently that appears to be the case. But I'm having a really hard time determining pH of 7.5 with the three different API pH tests. The wide range pH test seems the best but it's really hard when it's between say 7.0 and 7.5. So I did take a look at the CO2/KH/pH charts you mentioned. I'm not injecting CO2 so I thought they weren't helpful? But what is interesting is I should have better CO2 levels (even with no injection) if I can get my KH and pH down to more reasonable numbers. So I could possibly increase agitation with lower KH/pH and not worry so much about losing what little CO2 I do have in there.

On a related note in terms of philosophy (and this is contrary to a lot of advice) -- I personally see no purpose in mixing RODI water with tap water, unless you are trying to save small amounts of money. The main reason for using RODI water for most people is to take control of their water chemistry, to not have to worry about whatever is in their tap water.

So if you are mixing RODI with (say) 50% tap water, what you are doing is taking only 50% control over your environment, but going through all the trouble of an RODI system to do so. For pennies more and a bit more run time, you get to take 100% control.

So why bother?

Absolutely agree with you on the above. So glad again to know what I was feeling and thinking is being done by others. I have hung on to the idea that I needed to have some level of well water in there for two weeks. (My latest variations included 7:1 and 9:1 RO:Well combinations) I was trying so hard "to it make work" but you are so very right "why bother!" indeed! So I'm moving in other direction with my tests. Hoping now for some better results. If I was more experienced with the fish part and had a bigger tank, my well water might be perfect for some cichlids. Maybe someday!

Thank you again Linwood! I really appreciate your post!