RO water pH

[sickboy]

So I've had my tank running for 3 weeks now and one of the biggest problems I've had, other than the stupid green algae, is that I have a low pH. It was around 7.6 or so, until I started adding this buffer that my lfs suggested. That has brought it up to 8.2 so everything is ok, but I was just doing a top-off and decided to test my RO water. It was 6.4! This can't be normal, can it? Pure water should be 7. Is this part of my problem? I'm using Reef Crystals for salt, is this the problem or is it my water? I get my water at a local grocery store for $0.08/gallon but am thinking that I should start paying a little bit more.

 

[the egregious]

I go to walmart and buy water that is purified by "electrolic reverse osmosis" @ 0.72 a gallon. The PH is usally always 7.1-7.3. Are you using the "fill up" station to get your water? if so that might be the cause. Sometimes those fill up stations are worse than tap water haha, depends on where your from.

 

[scsinet]

It's all about alkalinity.
RO water is stripped of nearly all alkalinity. Alkalinity builds and stabilizes the pH of water. Without it, the pH can vary wildly with slight changes in oxygenation. My RO water is stored in a large tank that's elevated off the floor with a valve near the bottom so I can fill a 6 gallon bucket. When I fill it, and the water pours in, the pH drops from about 7.4 in the tank to 6.0 in the bucket. If I let the bucket sit for a few minutes, it slowly rises back up. True story.

Anyway my point is that the pH of your topoff water is of little concern. If your tank is properly buffered, the tank will correct itself as you add water.
pH isn't really a controllable parameter of your tank, it's the result of other parameters. Redox, dKH, etc all play a role. If your alkalinity is correct and your big 3 (ammonia, nitrites, nitrates) are all in check, your pH will automatically be correct.
So I wouldn't worry about it.

 

[lexluethar]

I would definately be purchasing higher quality water, and then properly mixing the water for 24 hours. I believe the RO water I purchase is 40 cents a gallon and it usually has pretty low PH. But once I mix in the salt and allow the water to mix w/ a powerhead for 24-48 hours the PH rises to around 7.8 ish. You need to have your PH placed to where it is mixing the salt, but also displacing the water on the surface to allow oxygen into the water.
I agree with SCSI though, like always...
Your tank is so new you just need to make sure your big 3 are in check, and using the proper buffering things (naturally) like your sand and water movement and you'll be fine.

 

[bang guy]

IMO it's Carbon dioxide that can easily lower the PH of RO water. There's no reason to be concerned about the PH of your fresh water source. As long as it's pure water the PH is irrelevant.
I would caution against adding "buffer" without testing your Alkalinity. If your Alkalinity is normal or high then adding a "buffer" can cause water parameters to become unbalanced which will cause major problems.
I say "buffer" because what the LFS suggested is actually an Alkalinity additive, not a buffer. Low PH is a symptom and blindly increasing Alkalinity is not solving the problem, it's masking the symptom.

 

[sickboy]

Thanks for the responses. The big three have been in check so far, I have even been bringing samples in to get tested because I didn't believe my tests, but in that regard all is well. The only way I have to test alkalinity is through dip strips. I need to get a new test for this but haven't yet. But the buffer is a two part additive that has raised the alk from about 150 to around 300. Sorry I can't be more accurate.
So what would be the long term fix? I have a 38 gallon, with 45 lbs. of Tukani rock, and 20 lbs. of Carribsea Agro-live sand. I just have 5 snails and 10 crabs to help me control the algae. For water movement I have an Emperor 400, two Koralia 2's, and a Prizm Deluxe skimmer ( I know they suck, I just needed a cheap one for now. Plan on getting a better one in 4 months or so). Any advice would be much appreciated.

 

[bang guy]

You have good waterflow, that's great! So, that's not the problem.
Assuming your trace elements are balanced the low PH is probably caused by either excess CO2 in the water or organic acids from decomposition.
Excess CO2 can be caused from an inadequate skimmer, insufficient gas exchange because of a sealed tank (glass cover), overstocking, excess algae, or simply high CO2 levels in the room the tank is in.
Organic acids show up if there is a clogged mechanical filter, an organism has died and not removed or eaten, or detritus is collecting somewhere in the system.
I am curious what the 300 ALK means. If it's 300ppm carbonate then that's excessively high and could cause PH problems from precipitating Calcium carbonate.

 

[sickboy]

It says "Total ALK (KH) ppm". I just got paid Friday though, and the first thing tomorrow I'm getting a new test kit for ALK/Calcium if I can find one.
According to the chart with the dip strips, it say 300 ppm total alk is "ideal." Is this correct?

 

[bang guy]

Originally Posted by sickboy
http:///forum/post/2639443
It says "Total ALK (KH) ppm". I just got paid Friday though, and the first thing tomorrow I'm getting a new test kit for ALK/Calcium if I can find one.
According to the chart with the dip strips, it say 300 ppm total alk is "ideal." Is this correct?

IMO 175ppm is a better ALK level. I'm not familiar with using test strips though. Maybe they use a different scale than what I'm thinking of.