pH low and can't seem to figure out why

Jpharr · #1 04/25/2006, 06:36 PM

I have been having problems since my tank began keeping my pH in what I consider an acceptable range. I would like my tank to run between 8.2-8.4 during the day and no lower than 8 at night. However, my system consistently hits 7.8 at night and 8 during the day. I know about the diurnal swing and understand this concept. I have done the aeration test, and the pH does not change with either test (indoor or outdoor). My most recent attempt to bring it up is to top off with limewater, and it gives a short lived spike, but then it falls back to the original level before I top off again. I use oceanic salt and RO water.

Current par
Ca--500
Alk--3.2mEq/L
Mg--1500
SpG--1.026
PO4--undetectable
O2--7
Nitrate--undetectable
NH4--undetectalble
All test are salifert

Here are a few questions:
How do most of you mix up your lime water?
If you use a Ca reactor (I do) do you still top off with lime?
What is the pH of your effluent (mine is 6.8)?
Thanks for any ideas in advance!

Jpharr · #2 04/25/2006, 07:17 PM

Okay, I have done some more investigating, and I think I may have found a significant part of the problem. As I stated I have been using oceanic since the beginning of my tank, and I have loved it. However, I have made up a batch, and the pH is 7.8. That is after 24 hours of aeration and circulation. Any ideas why this salt mix is testing so low? Any ideas on how to correct it? Any suggestions on another salt? I would be willing to consider anything other than IO. I used it once and just didn't like it. No offense to all of its advocates. Thanks again for your replies!

ced · #3 04/25/2006, 07:20 PM

Is the tank open top?
If not, you should open it during the day: it allows the CO2 to go out.
I am using a very cheap DIY Ca reactor for my kalkwasser:
1 cheap level pump, 1 1G water bottle, 1 10 galon bin, 1 timer and 1 level switch.
I put the calcium hydroxide in the bottle, the pump between the bottle and the bin (full of RO), and the water exits the bottle to go to the tank. That way, the lime water is never in contact with the air (very important).
I shake it every morning, time-out the pump for 5 hours (to allow the kalk to dissolve), and here you are. (my Ph oscilates between 8.2 and 8.4)

Jpharr · #4 04/25/2006, 08:38 PM

Yes the tank is open top. I understand what you are saying with your kalk system. Sounds unique and simple. I have been mixing my kalk up in a 5 gallon bucket 1 heaping tablespoon to about 5 gallons of water. I cover it so that it is not exposed to air. Does anyone have a more scientific way of doing it?

Is anyone out there using a pH controller in the following manner. Here is my idea. First, I can't help it, I like my Ca reactor. So this is what I am thinking. Set the activation point of the pH controller at 8.3 with a +- scale of 0.1. Which should keep the pH between 8.2 and 8.4. On the high side I would have my Ca reactor on and when it drops an aqualifter pump would kick on to drip kalk into the tank. Any and all opinions on this idea are welcome!

DrBDC · #5 04/25/2006, 09:49 PM

Many with ca reactors will use lime to correct the pH drop caused by the ca reactor. In fact it could have a double benefit in that you can get a pH increase from the lime and you'll be able to dial back the ca reactor as well further reducing the pH drop. To saturate the limewater use 2 teaspoons per gallon and cover. Use a dosing pump vs. just adding it and and you can just run it at night if you need to. Also reverse lighting on the fuge will help with nightime pH drops if you have macro growing in it.

What brand calibration solutions are you using? Many low pH problems are actually calibration solution errors.

Here's a couple articles on low pH and calibration solutions:

http://www.reefkeeping.com/issues/2004-09/rhf/index.php

http://reefkeeping.com/issues/2005-02/rhf/index.php

bertoni · #6 04/26/2006, 01:03 AM

I agree that double-checking the pH kit is in order before making changes. I'm a bit suspicious of it at this point, since I haven't heard of pH problems with Oceanic and the aeration test didn't show indoor CO2 issues.

If the pH is correct, a 24-hr lime drip for autotopoff should help some. Also, a reverse-lighting refugium could help. The alkalinity level is fine.

Jpharr · #7 04/26/2006, 02:01 AM

I have a pinpoint monitor, and have thus been using their brand of calibration fluids. I will take a look at those articles. The reverse lighting does not seem to have much of an effect on the pH. I have been doing that for a while. Thanks for the ideas. I have been topping off with lime for 2 days now, and my pH keeps wanting to drop back off.

By the way, do any of you do anything special to your RO water before you mix up your salt? I have heard that the RO water can actually decrease your pH.

DrBDC · #8 04/26/2006, 05:59 AM

You don't need to do anything to the ro/di water first. If you take a pH reading on ro/di it can be all over the place since there is nothing to buffer it. Sticking your hand or even residues on the pH meter could potentially affect it. Once you add the salt mix it will stabilize the pH.

Is there any macro growing in your sump? I'm not sure the reverse lighting would help w/o macro in there. It may some but not effectively. Is this the tank in your signature that has been running 18 months?

Can you cut back on the drip rate from the ca reactor and add more lime to the topoff water? Also, is the pH probe far enough away from the output of the ca reactor with a good current/mixing after the output?

mikeatjac · #9 04/26/2006, 06:16 AM

I arate my RO water for a day to drive off the co2.

DrBDC · #10 04/26/2006, 07:55 AM

You need to do that when you mix the salt anyway. I use a maxijet with the air pump. Usually for almost a week but it "should" be for a day to ensure full mixing.

Randy Holmes-Farley · #11 04/26/2006, 09:36 AM

Try the aeration tests in the low pH article above. The low pH is caused by excess CO2, and the tests help diagnose where it is coming from.

Jpharr · #12 04/26/2006, 09:46 AM

Okay, I will repeat the aeration test and see what happens. I have mixed up salt aerated it for 24 hours and the pH is 7.8. It almost seems like the batch of oceanic that I have been using for quite some time now doesn't have enough alk in it. Ca is at 500 in freshly mixed water and alk is at 2.4mEq/L. I poured 1 qt of lime water into the 10 gallons to simply raise alk (and Ca proportionally) in order to increase pH. The pH jumped from 8.8 then returned to 7.8 over night. I do not know how the house could have a high CO2 content given that my O2 test out at 7.

Randy Holmes-Farley · #13 04/26/2006, 09:49 AM

Make sure you do the test with a cup of water only, and do it with inside and outside air.

Low alkalinity will contribute to low pH, but alkalinity above 2 meq/L will not cause the pH to be below 8.1.

CO2 and O2 are unrelated. Both can be above normal, or both below normal, or....

Jpharr · #14 04/26/2006, 09:49 AM

Oh yeah to answer the Macro algae question. My sump used to contain caulerpa, and I light it on a reverse cycle. However, it had little to no effect on pH. As noted above my PO4 is 0 and thus it really didn't grow well. When I upgraded my skimmer, it all simply died, I assume because my nutrients were so low.

Jpharr · #15 04/26/2006, 11:45 AM

Okay repeat aeration is complete with some suprising results. Both cups started out at 7.93. 1 hour later the outside cup rose to 8.19 while the inside cup actually dropped to 7.88. I guess all that weather stripping really does work. We don't smoke, and are constantly coming in and out of the house. So now that we know that the inside air is laden with CO2, I have to come up with a treatment plan, and I am coming up a little short.

I can't find away to easily aerate the aquarium with outside air. We live in the south so insecticides could become a particular problem.

Simply opening a window would help equalize the air, but then the temperatures here would cause that to be a disaster. I have thought about somehow pumping air in from the atic, but that seems amazingly complicated.

Has anyone tried using multiple house plants to remove the CO2. Of course, this maybe like shooting a bb gun at a tank.

By the way Randy, I love your articles. I am an avid reader, but this one through me for a loop, because the first aeration did not cause significant changes. However, I have since recalibrated my meter. Thanks again to everyone. If someone has an easy way to fix this please let me know. Right now it is looking like limewater and Ca reactor on a pH controller. I have concerns that I may end up adding so much limewater that I overflow my sump.

Jpharr · #16 04/26/2006, 11:49 AM

Sorry I am being so long winded, but I have just completed some more test. I have turned my Ca reactor down, and it is now sitting at 7. I have been topping off (one pitcher at a time) with lime water now for 3 days. Here are my new readings.
Alk--3.6 mEq/L
Ca--540
I was afraid of this with the additional lime water additions. Is there a way to (cheaply) to set up a lime drip for topoff?

Randy Holmes-Farley · #17 04/26/2006, 01:49 PM

Okay repeat aeration is complete with some suprising results. Both cups started out at 7.93. 1 hour later the outside cup rose to 8.19 while the inside cup actually dropped to 7.88.

That's what most folks find: elevated indoor CO2.

Limewater and fresh air are the only really effective options. You can drip limewater with a home made or cheap dripper. I discuss options in this article:

What Your Grandmother Never Told You About Lime
http://reefkeeping.com/issues/2005-01/rhf/index.htm

How much added water can your sump hold? How much do you evaporate each day?

By the way Randy, I love your articles.

Thanks.

Jpharr · #18 04/26/2006, 02:15 PM

My sump probably could squeeze in an additional 2 gallons. I typically evaporate between 1 and 2 gallons/day out of my system. I estimate with sumps and all I am running about 100-110 gallons. Randy, would you recommend a drip line similar to what used to be used on IV lines or would you recommend using a pH controller with a very small pump like the aqualifter? I have learned to easily alter the output of these little pumps with head pressure, which is why I think it might work. Thanks again, for taking the time to answer all of our chemistry questions. I have now read all of your articles on pH that appear in RK magazine and enjoyed them all. I must say at I am now at the least wiser on pH issues. Thanks again!

Jpharr · #19 04/26/2006, 05:10 PM

I don't want to count my chickens befor they hatch, but it appears that Randy hit the nail on the head. I still don't know why my first aeration test gave inconclusive results, but the second was clear.
Here is my current solution.

I had an old Prizm laying around that isn't worth much, but it will mix air and water. I simply ran a piece of airline tubing through a hole in the ceiling that was already there (phone line) and connected it to the air intake of the skimmer. This pulls air from the attic (outside air) into the skimmer and mixes it with the tank water! Thus, I now have aeration from outside air. I now just have to work up a charcoal filter. Any ideas on this one? 3 hours later and my pH is sitting at 8.1 and rising slowly.

Just thought I would update in case anyone was tagging along.

bertoni · #20 04/26/2006, 06:44 PM

That sounds like a good solution to me! I can't help with the charcoal filter, though.

Randy Holmes-Farley · #21 04/26/2006, 07:31 PM

I agree thaty is a fine solution.

I deliver limewater from an 88 gallon reservoir with a very slow pump (a Reef Filler) controlled by a float switch in my sump.

Jpharr · #22 04/29/2006, 07:39 PM

Okay, I have ordered a float switch and plan to top off with lime water. pH values have improved, but are still not where I want them. They are steady at about 8.1.

I think I have come up with a way to install a charcoal filter inline. I have an old prefilter for an aqualifter pump. I plan on taking the cotton out of it and packing it full of carbon. This will be attached to the end of the airline in the atic, so that all air will first have to pass through the charcoal before coming into the skimmer and finally the tank.

Randy Holmes-Farley · #23 04/30/2006, 07:08 AM

The trade off will be how much it drops the air flow vs how much useful purification of the air it will do. At least the air flow is easy to check on.

Jpharr · #24 05/01/2006, 11:30 AM

Randy, that's a good point. I have had another thought. If I am pulling air from the outside with my little prizm, but my AquaC180 is pulling air from the inside, will this not offset outside air aeration? Or will this eventually pull down the CO2 levels of the house since the tank will eventually reach equilibrium?

Randy Holmes-Farley · #25 05/01/2006, 11:45 AM

The more indoor aeration there is (including the tank top) the harder it is to raise pH this way. Some folks find that a skimmer drawing outside air has little useful effect against the indoor CO2 entering the tank continually through the top.