RO/DI water has LOW pH

[azfishgal]

Is this normal for everyone else? My tap water is 7.6 pH, but after it goes through my RO/DI system it's 6.0!

Is this normal? I actually didn't realize this until a few days after I started using it. I tested the TDS but didn't think about the pH, until I was working on lowering the salinity in my QT. So now that I know my RO/DI water is so low I need to add a buffer to it every time, before I top off my DT. But I also need to add calcium every day, but understand it's not good to add both a buffer and calcium at the same time. How do I solve this problem? Should I just not add a buffer in the morning (when I add my calcium) and then add a little more than normal buffer at night when I top off? I have to add almost a gallon in the morning and a gallon at night.

 

[cmaxwell39]

That's strange. The ph of pure water is 7.0 so I don't understand why the ph of your RO water is lower than that.

 

[earlybird]

Yep RO water has a low ph. Almost everything that helps it buffer has been removed. Normal.

 

[larryndana]

so what besides salt should be added to bring it up? i'm curious as well. just a regular buffer?

 

[azfishgal]

Originally Posted by larryndana
so what besides salt should be added to bring it up? i'm curious as well. just a regular buffer?
That's what I'm doing now when I top off, adding some buffer to my RO/DI water before I put it in my tank. I wasn't at first and then after I realized how low the pH in my RO/DI water was I tested my DT and my pH was 8.0!

When I mix my salt (Reef Crystals) with my water it's fine, pH is 8.2. So it's just when I top off with straight RO/DI water that I now seem to have a problem. Does anyone else add buffers to their RO/DI water before they add it to the DT?

 

[earlybird]

Originally Posted by azfishgal
That's what I'm doing now when I top off, adding some buffer to my RO/DI water before I put it in my tank. I wasn't at first and then after I realized how low the pH in my RO/DI water was I tested my DT and my pH was 8.0!

When I mix my salt (Reef Crystals) with my water it's fine, pH is 8.2. So it's just when I top off with straight RO/DI water that I now seem to have a problem. Does anyone else add buffers to their RO/DI water before they add it to the DT?
I drip my top off water so it doesn't matter too much as it goes in very slowly. Could buffering the ro water throw off the alk in the tank when added?

 

[azfishgal]

Well, now I'm running into another problem.

I just got my new Salifert test kits in and this is what my tests came out to be in my DT:
pH 8.1
Alk 5.26 (dKH 14.7)
So now how do I raise the ph without raising the Alk, because as of right now, isn't it to high?!
In my QT my pH is 8.0 and my KH/Alk is off the charts!!! So what now? How do I bring down the alk without bringing down the pH?

I have been using Kent Marine Supperbuffer-dKh and all has been well, or at least I thought. Should I use two different buffers now, one for pH and one for Alk? Do they even make something like that?
I thought I had this balancing act finally figured out, now I'm more confused than ever.

 

[moneyman]

Originally Posted by azfishgal
pH 8.1
Alk 5.26 (dKH 14.7)
So now how do I raise the ph without raising the Alk, because as of right now, isn't it to high?!
pH is fine. Alk will drop. Check your calcium level.
Only H2O evaporate from your tank. So, you only want to pour H2O back into your tank. Your RODI is mostly H2O. If you start to put buffer (alkalinity) into your RODI, your tank will increase in alkalinty.
It is normal for RODI to have low pH.

 

[azfishgal]

Originally Posted by MoneyMan
pH is fine. Alk will drop. Check your calcium level.
Only H2O evaporate from your tank. So, you only want to pour H2O back into your tank. Your RODI is mostly H2O. If you start to put buffer (alkalinity) into your RODI, your tank will increase in alkalinty.
It is normal for RODI to have low pH.
My calcium is 410. With my top off water having a pH of 6.0, won't that lower my pH in my DT. At least it seems to be after testing my DT.

 

[sjimmyh]

Read up on CO2. Water absorbs it readily, it forms carbonic acid and drives pH down. Your pure water (pH 7) absorbs CO2 and whallah, ph 6.

 

[larryndana]

your alk and cal are high enough.
and how are your other parameters?
the nitrogen cycle effects ph. this is from what i've read, also ph is measure of hydroden ions....i'd have to go back and read some more, but the nitrogen cycle takes up these ions which effects ph.
how much flow do you have?
i don't remember how flow effects it, i know better flow allows for more gas exchange. which is good since the gas thats removed is carbon dioxide which algea, bacteria, and fish all release into the water. not sure now if carbon dioxide is related to ph or not, just in the same chapter i was reading.
i'm adding more flow to my tank now, maybe more lr for more biofiltration.

 

[larryndana]

Originally Posted by larryndana
so what besides salt should be added to bring it up? i'm curious as well. just a regular buffer?
i'm still interested in what people are adding to their fresh and mixed water.

 

[azfishgal]

Originally Posted by larryndana
your alk and cal are high enough.
and how are your other parameters?
how much flow do you have?
i'm adding more flow to my tank now, maybe more lr for more biofiltration.
Well, my Ammonia and Nitrites is at 0, but my Nitrates are a bit high at 20. I was doing a water change every two weeks (12-15 gallons), but I think I'll bump it up to every week until every thing evens out, then I'll see if I can move it to every 2 weeks.
My flow rate is 2,575 gph, so my 125 gallon tank turnover is 20xs per hour. Now not sure if some people count the return pump lower than what it says because it's going up about 4' before it get's into the tank, but this is what I have: Two powerheads on each end of the tank at 850 gph each, then my return pump is 875 gph (I don't count my skimmer pump that's in the sump). Even if my flow slows down by the time it gets up to my DT I still think my flow rate is good. I have worked hard to make sure I have no dead spots in my tank, and as far as I can see I don't.
As Jimmy suggested, I'm starting to reseach the C02 factor and how it relates to our tanks balance.

 

[larryndana]

everything seems ok.
i'd be interested in more about carbon dioxide as well. all i read is better flow.

 

[azfishgal]

Originally Posted by larryndana
everything seems ok.
i'd be interested in more about carbon dioxide as well. all i read is better flow.
edit** PLEASE do not advertise for other baords its agianst the rules** I've been told there is a chemist on there that answers a lot of questions regarding this issue. Also, Jimmy did a good job explaining the CO2 factor in another thread I started:
https://forums.saltwaterfish.com/t/273729/ph-to-low-alk-to-high

 

[larryndana]

Originally Posted by azfishgal
Go to ****. I've been told there is a chemist on there that answers a lot of questions regarding this issue. Also, Jimmy did a good job explaining the CO2 factor in another thread I started:
https://www.saltwaterfish.com/vb/showthread.php?t=273729
thanks.

 

[michaeltx]

Originally Posted by larryndana
i'm still interested in what people are adding to their fresh and mixed water.
I do not add anything to the top off water and when I do water changes the salt mix has everything that is needed to buffer and add in the trace elements for the tank. I also do not add anything that I can not test for like iodine or magnesium etc.. etc..
Mike

 

[briand7878]

Make sure you dont do a fresh water dip with ro/di water....learned that the hard way. The alk will and did kill my fish.

 

[larryndana]

Originally Posted by MichaelTX
I do not add anything to the top off water and when I do water changes the salt mix has everything that is needed to buffer and add in the trace elements for the tank. I also do not add anything that I can not test for like iodine or magnesium etc.. etc..
Mike
thanks. what salt do you prefer?

 

[michaeltx]

I used IO for years and on my last tanks I decided to change to a different brand to see what kind of differences I could see. I am hooked on red sea salt right now. The next tank I setup I am going to use another brand not sure which though.
Make sure you dont do a fresh water dip with ro/di water....learned that the hard way. The alk will and did kill my fish.
Freshwater dips should only be thought of as a last resort and are not suggested as a regular treatment of anything because it will stress the fish out really badly. Proper QT and hypo or other meds in that tank will insure that you dont introduce ich into the systems.
Mike