pH/Alk Advice Needed

[Zen685]

I have a 2 year old 24 gal Aquapod stocked with soft corals and a couple of fish. I've noticed that my pH has steadily dropped over the last 6 months and has been taking larger swings from day to night. My alkalinity has dropped to around 7 dKH so I assume this is the reason for my pH problems. What causes my alk to drop and how to do i get this under control? I've read that dosing kalkwasser helps but I've never heard of doing this on a tank this small so I'm a little hesitant. Any ideas?

[Percula9]

The pH usually drops based on the amount of CO2 in the atmosphere. I agree the alk could come up a little. Raise alk with baking soda or a fish store commercial alk buffer. During the day prop open the top of the pod to increase gas exchange. Does the tank have a protein skimmer?

[Zen685]

Thanks Perc. No protein skimmer or sump. I have an area in the back with chaeto. I'm not convinced it's only a CO2 problem. I've areated and opened the hood which helps a little but not enough. The tank sits near my back door which I open regularly to let my dogs out so there should be plenty of fresh air. That's why i'm leaning towards an alk problem.

[Origami2547]

Alk could be consumed as part of the natural biological processes in your tank. Do you perform regular water changes? What mix?

Are you sure that your test kit is accurate?

Finally, if you take a cup of your water out and aerate it in fresh air, you can check to see if there's a pH rise. If so, you've got CO2 issues. If not, you can eliminate that from the list of possibilities.

[Zen685]

I do weekly 10% to 20% water changes with Instant Ocean salt. The test kit is an API which is usually pretty good. It accurately measures the rise and fall from night and day so I don't think anything is wrong with it unless the scale shifts over time.

I just bought an air pump and stone to test the CO2 theory this morning. I'll let you guys know what I find out.

[Percula9]

Try seachems Reef Buffer. What is the pH? The pH can vary any where from 7.8 in the morning to 8.3 in the late afternoon. The pH swinging over time is normal, it's rapid changes in pH that are not good. If your livestock is healthy then I wouldn't worry about it to much. Try the Reef Buffer. What is the alkalinity of newly mixed water?

[Zen685]

Perc: The pH stays around 8.0 in the day and drops under 7.8 at night. I went a couple of days without lights like I normally do every few months and the pH tested off the scale low which is why I decided to jump on the problem. The fish and corals seem healthy but I've seen a stagnation in my coral growth since the pH/alk problem has come along. I'm blindly hoping this will help. When I setup the tank in Feb of 07 corals grew normally. Now two years later, I can't get anything to grow. pH and alk are the only parameters that I've found are off.

I tested the newly mixed water that's getting ready to be used for a water change and it tested at an alk of 8 dKH and a pH of around 8.4. The alk seems low for fresh salt water. I may have gotten a bad salt mix.

C02 test update: I put a quart of tank water in a cup and put an air stone in around 30 min ago. The pH has already gone from 7.8 to 8.4. I think that settles the low CO2 issue. Now I have to figure out how to place that air stone in my tank without getting bubbles in the display.

[Randy Holmes-Farley]

This article has more on using air (inside air or just aeration) to raise pH:

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

[Zen685]

Thanks Randy. I've been following that article and the one on calcium and alkalinity. Should there be a lag in the alkalinity rise with respect to the pH rise? My pH has gone up steadily all day to 8.4 since I added the air stone but the alk has stayed around 7dkH and calcium is around 300ppm.

Could all of this be caused by the abundance of coralline algae and thus calcium usage in my tank? I've never dosed anything over the 2 year life of the tank.

[Randy Holmes-Farley]

Lag when dosing what?

Coralline will consume alkalinity (and calcium) but not lower pH. :)

[Zen685]

I've been dosing air all day. :) It got rid of the excess CO2 and brought the pH up but the alk has stayed low. If the two are linked is there a lag in the relationship between pH and alk?

I'm starting to realize that I'm trying to solve two different problems; low pH due to excess CO2 and low calcium due to excess coralline.

Here's a picture of the tank we're troubleshooting.

<a href="http://s619.photobucket.com/albums/tt273/Zen685/?action=view&current=DSC00571.jpg" target="_blank"><img src="http://i619.photobucket.com/albums/tt273/Zen685/DSC00571.jpg" border="0" alt="Photobucket"></a>

[Percula9]

Instant ocean is low in calcium and magnesium. I recommend Seachems Reef complete. This will raise calcium and maintain magnesium and strontium. A calcium of 300ppm is to low. You might try Randy's DIY two part or buy a two part from the fish store. I'm glad you solved your pH problem. Raise the alk in balance with the calcium.

[Origami2547]

<a href=showthread.php?s=&postid=14288457#post14288457 target=_blank>Originally posted</a> by Zen685
My pH has gone up steadily all day to 8.4 since I added the air stone but the alk has stayed around 7dkH and calcium is around 300ppm.


Glad you got your pH question answered.

Both your alk and calcium are low. If these are accurate numbers, it could just be the result of consumption. Though, with regular water changes, I'm somewhat surprised that they're this low. The IO that I mix up normally measures out to about 380 ppm on calcium, 9 dKH on alk, and 1060 on magnesium, so I supplement my change water with every batch. You could boost both your alk and calcium rather easily and inexpensively using calcium chloride and baking soda (sodium bicarbonate) over a few days. (Take care not to add both back to back.) If I had to guess, I'd bet that your magnesium levels are a bit low, too.

[Randy Holmes-Farley]

I've been dosing air all day. It got rid of the excess CO2 and brought the pH up but the alk has stayed low. If the two are linked is there a lag in the relationship between pH and alk?

Aeration has no impact on alkalinity, so you'll need to up the dosing if it is low. :)