Ph and Alkalinity

Lenair Stevens · May 7, 2016

I moved and set up a 90 gallon tank 10 months ago. Since the beginning my ph has run a little low (7.8-7.9). I started dripping kalk 3 days ago and my ph has gone up to 8.2 but my alk which I was having to dose 2 part to keep at 8.4-8.8 has gone up to 10.5. Is there anything i can do to keep the ph up and not raise my alk. My calcium is at 420 and my magnesium is at 1340.

Any suggestions would be appreciated. I am running a large protein skimmer and a GFO reactor.

mcarroll · May 7, 2016

pH generally has a daily cycle where it peaks around lights-out (photosynthesis having used the available CO2 from the water) and bottoms out right around lights on (after the whole tank had all night to respire CO2 into the water).

When were you measuring and do you know what your day/night range was?

Unless something was observably wrong with the tank or some critters before, my advice would be to stop worrying about the pH and stop dosing kalkwasser.

Lenair Stevens · May 7, 2016

My ph was peaking with lights on at 7.8 and when lights were off except for sump it would get as low as 7.6. Corals seemed fine except for an elegance I have had for 2 months. It seems to like the higher ph.

mcarroll · May 7, 2016

Run (more) macro algae (or brighter lights) in the sump at night to help. I'd bring the sump lights on around an hour before the main lights go out and turn them off about an hour after the main lights come back on in the morning. Based on your numbers, I wouldn't worry beyond that.

And I hate to say it, but as long as the rest of your tank looks happy, I wouldn't try too hard for the elegance. They're notoriously hard to keep happy or even alive regardless of pH, and you don't want to end up tweaking your other corals in chasing pH for that one.

Lenair Stevens · May 7, 2016

Thank you.

Downbeach · May 8, 2016

Are you using a pH buffer? If so, contrary to advertising, this will/can be elevating your alkalinity. What are you using to measure your pH with? If its a chemical kit or strip, you can use the reading to determin a trend, but I wouldn't rely on them for great accuracy. Can you run an air line from your skimmer air intake to an outside air source? If so, this will pull in air with lower concentrations of CO2, elevating your pH. FWIW, I ran a mixed reef for many years with a pH ranging from 7.8 to 8.1, measured with a properly calibrated Pin Point meter.

Lenair Stevens · May 8, 2016

Several months ago I tried a ph buffer but it caused the alk to rise so I stopped. For the past several months I had to do VERY little 2 part. My alk leveled out around 8.3-8.5 and my calcium at around 380-400. My ph would never go above peak above 7.9 at the end of my light cycle. Like I said, I started dosing kalk (4 days ago now) and my ph has gradually gone to a peak of 8.2 but my alk has gradually worked its way to 10.5. I thought (from reading) that kalkwasser would raise ph with minimal effect on alk. Now I don't know which is better --- lower alk with low ph or higher ph with higher alk. Reefing sure gets confusing!!

Downbeach · May 8, 2016

How much kalk are you adding? Are you considering your WC's in this trend? What salt mix are you using, at what SG?

Lenair Stevens · May 8, 2016

Adding 3 - 3 1/2 quarts a day as my top off. I do weekly water changes of 10%. Currently using Seachem Reef Salt and keep my salinity around 1.024 - 1.025.

At one point I tried adding a small air stone but really couldn't tell any difference so i removed it.

Downbeach · May 8, 2016

Is the kalk at full saturation(2tsp/gal)? Did you perform a WC in that 4 day window since starting to dose the kalk? If the CO2 in your system is in equilibrium with the surrounding atmosphere, adding an air stone likely will have little affect, which is why you want to bring air in from an outside air source with lower concentrations of CO2, or do something to use the excess CO2, i.e. adding/increasing your macro algae to help utilize more of the CO2, use kalk, etc. Kalk of course will add a balance of Ca and Alk, so along with an increase in pH you will see a bit of an increase in your alk and Ca(see here).

Lenair Stevens · May 8, 2016

Kalk is at full saturation. I did a 10 gallon water change on the 2nd day after I started dosing.Guess I will have to try and increase the algae. Can't really open windows and run AC / heat at the same time. Hard to try feeding outside air to the skimmer since the DT is on an inside wall.

Ontheway · May 8, 2016

Low ph and high kH is the worst

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Are you sure you double check calibration of pH meter? You may try sodium carbonate to upregulate kh which also slightly increases pH, if this is what you need.

Lenair Stevens · May 8, 2016

Ontheway --- maybe I said it wrong: I can have low ph and low alk or high ph and high alk. I did double check the calibration on the Milwaukee ph probe. Wish I could just raise the Ph. Will adding baking soda raise ph without raising alk?

Downbeach · May 8, 2016

No, plain baking soda will have a slightly lowering affect due to the CO2 it contains, but will add alk. The pH affect will be temporary, as it will go back to its base level once the system reaches equilibrium again. Soda ash will have a slightly elevating affect on pH, but again the pH will go back to it base level once the CO2 has reaches equilibrium again. They both will increase your alkalinity.

Lenair Stevens · May 8, 2016

Back to square one!

Waterjockey · May 8, 2016

I'm in the same boat. High(er) Alk, and lower pH....I'm fairly certain it has a *lot* to do with indoor CO2, as I get a slight rise in pH with the windows open (We've only had 3 days of weather where I can open the windows so far this "spring"). I was using Sodium Carbonate?(baked baking soda) sparingly as such a tiny amount has a huge, and immediate effect in my little 40 gallon system. I don't think the big swings are any good for the reef, so I have started dosing kalk just the last few days and slowly ramping up....and firat thing I noticed so far, is how much more stable my Alk is, and pH swings are smaller. I run an air pump to my needle wheel skimmer inlet (cheapie skimmer that runs great with additional air feed), and a stone in my sump, so I need to build an air-tight box to put my air pumps in, and then run a hose to the outside so the airpumps get fresh air. I am going to continue dosing small amounts of kalk (about 1/3 of my makeup water), just for the stability it appears to provide. I am now at pH 7.9 on average (was 7.7), with 10dKh, 420 calcium, 1360 Mag. I made sure my mag and calcium was at target before dosing. If I can hold at 10dKh, I'll be happy. I think I worry more about pH than is warrented

Cheers!