pH low and can't seem to figure out why

[Jpharr]

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]

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]

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]

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]

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]

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]

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]

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]

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

[DrBDC]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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

[Randy Holmes-Farley]

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]

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]

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]

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]

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.

[Jpharr]

I still need the help of the experts! I have good news. My pH is now very stable. The problem is...it is stable on the low side. It was fluctuating from 7.8 to 8.3. Now it is only fluctuating between 7.8 and 7.95 24/7. I now am using limewater to topoff via a float switch. I am so glad I finally got an automatic topoff system! Anyway, any ideas on why it is still low. Below are the most recent test results taken yesterday. All used salifert.
Ca--495ppm
Alk--3.5mEq
Mg--1425ppm

Notes: My Ca has dropped below 500 for the first time since I started my tank. Mg has finally fallen below 1500, and alk is still somewhat stable. To further complicate matters. I had to switch to IO salt, however, I have put a max of 5 gallons in the tank becasue I daily 1% water changes. Please feel free to give ideas.

[Randy Holmes-Farley]

Bringing in more fresh air to the room would likely help, if the outdoor aeration test showed a pH rise but the indoor test did not. Did you ever do an indoor aeration test?

The limewater has how much lime in how much fresh water? How much added daily?

[Jpharr]

1. I did perform the test, and it showed that I had excess CO2
2. I am pulling air from the outside into the aquarium via prizm for about 1 week.
3. I am mixing 1 "heaping" tablespoon/5 gallons of fresh RO water.
4. I would estimate that the AT is pulling about 1-1.5 GPD.

Thanks for your reply!

[DrBDC]

That's pretty weak kalkwasser. If you increase it to 2 teaspoons per gallon does your ca and alk rise too much? After some more water changes with IO it will have the ca lower which will help the ca number. Maybe try pointing a powerhead at the surface and churn it up in the sump area.

[Jpharr]

DrBDC, when you say 2 tsp/gallon do you mean rounded or actual tsp. Because there are 3 tsp/1TBS. 2tsp/gallon would equal 10tsp or 3.3TBS. I imagine with the size TBS's I am using I am close to this, but I guess I could double the dose and see what happens. Go to 2 heaping TBS/5 gallons. Don't you love all of this scientific talk! :)

[DrBDC]

Shake them just a little and let it be almost flat maybe a little round because at saturation level the excess will just settle out anyway.

[bertoni]

I would increase the dose more gradually. Monitoring pH and alkalinity will also be important. Overdosing lime can be unpleasant for all involved. If you go to full-strength lime, I'd measure pH after 15 minutes, 30 minutes, 1 hr, etc., as well as checking every day for a few days.

[Randy Holmes-Farley]

It won't hurt if there is a little excess lime in the limewater. It will just sit on the bottom of the limewater container. If that is not enough pH help, you can also consider increasing the evaporation with fans.

[Jpharr]

I do continuous monitoring of pH via a pinpoint monitor. I have not had any wide fluctuations. I have my auto top off set pretty tight, so that it will never actually pull that much at one time. My thought behind this, is that it will act more like a drip. I fear that a 1 inch fall before the ATO is triggered could cause a drastic pH swing. Thanks again for the replies!

[Jpharr]

Randy, are you basically saying to simply increase evaporation to increase top off, which would add more lime, there by increasing pH. This makes since, but I want to make sure I follow the logic. Sharp thinking by the way!

[mthedude]

are there any other ways to add O2 to the tank?

What do people with very large tanks in newer homes do? I'm assuming a good option would be to install an air exchange sytem to the HVAC in the house to ensure a good supply of fresh air into the home?

[Jpharr]

Actually, mthedude, the problem is not O2 it is the excess CO2 that drives down pH. The excess CO2 in the home air is no different than the CO2 you "accidently" add via a Ca Reactor for example.

The HVAC idea is a good one, but I don't know how easy that would be to fix. Espesially, if you did not build the house yourself.

I have been opening the window in the "fish" room for the past few nights. Daytime temps are simply too high to raise it during the daytime. That along with the more concentrated lime seem (crossing my finges) to be doing the trick. When I left the house this morning at 0200. The pH was 7.99, which is high for a nightime pH in my tank.

[Randy Holmes-Farley]

Randy, are you basically saying to simply increase evaporation to increase top off, which would add more lime, there by increasing pH.

Yes.

are there any other ways to add O2 to the tank?

Adding O2 will not help pH. You need to drive out excess CO2. Both can be high at the same time. An air exchanger can help, yes, but is very expensive.

[mthedude]

I've been thinking of adding an air exchanger to my house, they seem to start at about $400 for a unit that would exchange the air in a 1500-2000 square foot house. Kind of crazy to think we'd actaully spend money on our house to support our reef habit, but people have spent $400 crazier than that I'm sure.

[Jpharr]

Well, you could look at it like this. $400 for an air exchanger. It would have to be good for your health, because it would get rid of "stale" air. Then with the increased pH of your tank your corals would probably grow faster because they could take up Ca/Alk easier. This would increase fragging rates, and at 20/frag, it would only take 20 frags to pay for it. Sounds to me like you are investing in your tank! :bum:

[Reefflections]

Where have you scene air exchangers starting at 400 bucks?Have any links?I go threw this every year,when have to crank up the AC.

[mthedude]

Ebay actaully has quite a few air echanger auctions last time I checked. I think I was on DIY or something like that and started checking prices. As always if you go to Lenox or something like that they'll sell you one that's too big for your house and install it for you for a nice chunk on change. It's actually a pretty easy install, just get some 2 inch or larger PVC, plumb one one to fresh air, another end to your furnace/AC air inlet, another line to your air outlet and add a power lead. Pretty easy DIY project if you can get to your HVAC system easily. Luckily I live in a burm home and all my house is 1 level and my HVAC is in my utility/laundry room and could be done very easily. I'll see if I can find a site that has good deals.

[mthedude]

I know we're not supposed to post ebay links but in the effort to advance the Reef Aquarium hobby and increase the life of our pets, I'll post this one;

http://cgi.ebay.com/Airiva-Heat-Recovery-Ventilator-air-to-air-exchanger_W0QQitemZ6057883684QQcategoryZ20598QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[johnmsct8astro]

i checked my ph ttonight and it is 8.0 nitrate is 0 nitrite is 0 and my ammonia is o i have been trying to keep my ph at 8.4 but iit keeps dropping i have sed buffer but you guys say it not good. So waht can i do to help this out any information will be beneficil. its a 55 gallon aquarium with a sump and two maxi pumps and a proclear skimmer and itsa reef tank. plese reply thnax john

[Randy Holmes-Farley]

Limewater are aeration with fresh air are the best ways to raise pH. IMO, pH can be anywhere from 8.0 to 8.5, and many folks with nice reef aquaria allow it to drop as low as 7.8, although I'd keep alkalinity unusually high if it drops below 8.0. :)

This article has more:


Low pH: Causes and Cures
http://reefkeeping.com/issues/2004-09/rhf/index.htm

[mthedude]

Randy, if PH is 7.8 and alk is on the high side, are there any long term negative effects to the tank? I'm assuming it's just harder to keep Calcium at an acceptable level is ph is low and Alk is ok?

Until I figure out how to blow off the excess CO2 in my tank I'll have to run at 7.8 ph and keep Alk high (which so far has not been a hard thing to do).

[Jpharr]

It is amazing what simply cracking a window will do. I have been opening the window in the "fish" room at night for about 1 week now. My pH is now consistently above 8.0 at night and reaches 8.25 during the day. I am much happier with this than I was with 7.8-8. Thanks for all of your help everyone.

[Randy Holmes-Farley]

Randy, if PH is 7.8 and alk is on the high side, are there any long term negative effects to the tank?

The lower the pH, the more stress it is on calcifying corals. That may be partially offset by higher alkalinity. At normal alkalinity, oceanographers are very worried by a drop in pH impacting coral reefs, and they are not talking about it going as low as 7.8.