raise tank PH

[bcjm]

My tank PH had been around 7.6-7.8 for more than 2 years since I started keeping sps. The PH did not change by aerating the tank water overnight using outside air. So it is not too much CO2 in the water. I did not know what else to try. Two weeks ago, I raised the magnesium to 1400 ppm and cleaned my kalk reactor completely and putting in new power. The PH was increased to 7.9 at the highest in a day. This weekend I increased the water flow (half of the returned water) to go through the refugium. Now the PH raises to 8.16 at the highest.

 

One more thing I like to try but not sure if it makes any difference. I run Ca reactor and Kalk reactor. Do you think by raising the PH slightly in the calcium reactor is going to help the tank PH? I understand that I may need to increase the effluent dripping rate so it could be a wash. But again, the effluet maybe saturated, raising the PH slightly may not affect the amount of calcium/alkalinity in the effluent. I have a PH controller set between 6.5 and 6.6 to control the Ca reactor.

[dakotasreef]

I have the same problem. My tank ph only makes it to 7.9 at the end of the light cycle. I gave up trying to get in any higher. I would not lower your reactor ph in fear you might turn your media to mush.

 

I have great color and growth and would not change anything.

 

Sent from my DROIDX

[bcjm]

I will raise the PH in the calcium reactor not lower.

I get so so growth but not good color.

[dakotasreef]

You could try that, but then will you be able to keep up with calcium demand.

 

Sent from my DROIDX

[Origami]

Is your pH probe calibrated? What is your alkalinity?

[bcjm]

I believe my PH probe is correct but I bought a new probe anyway. I am going to calubrate the tank PH probe and reactor PH probe. My alkalinity is between 9 and 10 dkh.

[Origami]

What brand of salt do you use? It's not Seachem, is it?

 

I ran some curves a while back (posting it here, somewhere), that related pH, alkalinity and dissolved CO2 under nominal (clean and in equilibrium with the surrounding gas environment) conditions. My curves didn't go as low in pH as you're describing, but for your alkalinity level and pH, the curves show that your dissolved CO2 is nominally well beyond 3-4 times the average outside CO2 concentration (which is around 378 ppm). It's possible, I suppose, that you have a high level of organics and organic acids in your water which might be consuming alkalinity. But my initial thoughts are to 1) verify the accuracy of your alkalinity test and 2) verify the accuracy of your pH measurement, before investigating other possibilities.

 

For example, until recently, I thought that my dissolved CO2 was close to 700 ppm (high indoor levels) given my alkalinity and pH despite drawing fresh air from my attic into my skimmer (making me think the air wasn't as fresh as I thought). Then, I found that my alkalinity test kit was actually giving me false readings that were significantly higher. When I corrected for the error, I found that my dissolved CO2 levels were much closer to 440 ppm, giving me more confidence in the value of drawing fresh air into my skimmer.

 

The graph, by the way, was this one:

 

I found where I posted the graph. It wasn't in a stand-alone post, but it was here. In that post, I describe how I came up with the curve re-posted above. I continued with an explanation of how I derived the curves a few posts later (here).

 

Here's a cool graph showing atmospheric CO2 trends at Mauna Loa Observatory, in Hawaii:

[bcjm]

I have been using IO but now switch to Brightwell.

 

Does the PH value in tank water only depend on the CO2 content and alkalinity?

[Origami]

I have been using IO but now switch to Brightwell.

 

Does the PH value in tank water only depend on the CO2 content and alkalinity?

It's complicated by other factors, but these are the variables that we look most closely at. Temperature, salinity, tank volume and surface area available for gas exchange, agitation, ionic balance, organic acid content, presence of CO2 consumers and producers (plants and animals), lighting cycle, and a whole host of other factors come into play.

 

Thus, the disclaimer given when I originally provided the graph - that the exact relationship from tank to tank may very, but that the general relationship remains the same.

[bcjm]

"Temperature, salinity, tank volume and surface area available for gas exchange, agitation, ionic balance, organic acid content, presence of CO2 consumers and producers (plants and animals), lighting cycle"

 

Everything you have listed above alter the CO2 content and alkalinity. If I measure the CO2 content and alkalinity for a given water sample, can the PH be determined based on the graphic you have posted previously?

[Origami]

"Temperature, salinity, tank volume and surface area available for gas exchange, agitation, ionic balance, organic acid content, presence of CO2 consumers and producers (plants and animals), lighting cycle"

 

Everything you have listed above alter the CO2 content and alkalinity. If I measure the CO2 content and alkalinity for a given water sample, can the PH be determined based on the graphic you have posted previously?

 

Yes, it all has an effect. Here's a run-down:

 

Temperature affects the solubility of gasses in liquid, including CO2.

 

Salinity affects CO2 solubility, too.

 

Tank volume and surface area affect the rate at which partial-pressure equilibrium can be achieved - once it's achieved though, it has no net effect.

 

Ionic balance is redundant with salinity - sorry for the double accounting. Borate alkalinity may factor into this, too. (That's why I asked about using Seachem salt - it's high in useless borate alkalinity.)

 

Organic acids counter alkalinity by essentially neutralizing it in your testing.

 

And finally, life forms that consume and produce CO2 in your tank affect your CO2 and, thus, your pH. That's why you have a diurnal swing in your pH from day-to-day. Lighting affects this, too, as plants, while they photosynthesize in the daylight, respire at dark. Thus, they are consumers of CO2 during the day, but producers of it at night.

 

Regarding your last question, you have missed the point I raised earlier. The positioning of the curves can vary a little from tank to tank as many variable can fluctuate. However, don't expect huge shifts. Still, it takes little to shift your pH by as little as 0.2 pH units. It can be, for example, the difference between opening and closing a window in the room where the tank is located. Because of the number of variables, it would be impossible to provide for all the parameters - you'd need a book. However, with certain assumptions on the minor variables, and assumptions about the stability and health of your tank, we can generate the curves shown.

 

I'm curious, by the way, as to how you would go about measuring the CO2 in your tank (as mentioned in your last post).

 

Reiterating my initial response, though: You need to validate the measurements your giving. Calibrate your pH probe (even new probes need to be calibrated!) and make sure you're getting a good reading from your alkalinity test kit. Without a calibrated probe, you can only detect shifts, you can't really pin down the reading. Get some reference solutions at your LFS. Both BRK and F&F have them. I'm sure others do, too.

[OldReefer]

If you want to try a CO2 scrubber for a couple weeks, I have one from BRS I am not using ( I ran a pipe to outside air for my skimmer). You could try it for a few weeks and just get me a replacement refill cartridge. My tank ran a pH of 7.8 - 7.9 until I got fresh air to it. Now I am at 8.2 - 8.3.

[Origami]

If you want to try a CO2 scrubber for a couple weeks, I have one from BRS I am not using ( I ran a pipe to outside air for my skimmer). You could try it for a few weeks and just get me a replacement refill cartridge. My tank ran a pH of 7.8 - 7.9 until I got fresh air to it. Now I am at 8.2 - 8.3.

It's even better than fresh air, Bill, you're bringing CO2-depleted air in if you're running fresh air through a scrubber.

[OldReefer]

I used both the scrubber and outside air for a while and then pulled the scrubber off. It didn't make much of a difference. It seems once you get fresh air to the skimmer, the scrubber was just "icing on the cake".

 

Now if you run a scrubber with inside air, I bet it would really have a big effect. It wasn't practical to do that before because media cost so much, but now BRS is selling bulk CO2 media pretty cheap.

[bcjm]

I ran the skimmer with outside air for a day and it did not make any difference to the tank PH.

[Origami]

I used both the scrubber and outside air for a while and then pulled the scrubber off. It didn't make much of a difference. It seems once you get fresh air to the skimmer, the scrubber was just "icing on the cake".

 

Now if you run a scrubber with inside air, I bet it would really have a big effect. It wasn't practical to do that before because media cost so much, but now BRS is selling bulk CO2 media pretty cheap.

 

It's really a matter of equilibrium. If the air around the tank is full of CO2, unless you're offgassing CO2 from the tank (in the skimmer because you're using CO2-depleted air) at a rate faster than it is restored from surface air-gas exchange, then you probably won't see much effect, or the effect would be transient. Now, if you could scrub the entire ambient environment, you could blow off the CO2 and force the pH up (effectively, you're changing the carbonate species distribution when you do this).

 

I ran the skimmer with outside air for a day and it did not make any difference to the tank PH.

 

Make sure your probe is calibrated and your test kits are accurate.

[bbyatv]

I have effluent that enters my tank with pH at 7.2 and alk at 32 dKH.

 

The pH in the primary chamber is set at 6.5.

 

This along with a Kalk stirrer allows me set my pH in the tank anywhere I like by adjusting the flow rate from one or the other. Both are on dosing pumps.

 

In order to get my pH up on my effluent, I run it through a second chamber of CRM and then into a 2 liter de-gas chamber. The effluent then overflows into my sump. I have an air stone in the chamber that blows off lots of the CO2.

 

Here is a picture of my setup:

 

 

If you can de-gas the effluent before it enters the tank maybe you can get the pH up?

 

I fought this problem for a long time and this is what finally fixed it.

 

Good luck,

 

Bruce

[Origami]

^^I love that picture, and the technical term "2-liter de-gas chamber" (which, by the way, receives less respect in the drawing where it's called a 2-liter soda bottle).

 

The OP noted that he's not getting any change in pH when he aerates tank water overnight using outside air. The implication is that he's already in equilibrium with the ambient CO2 levels.

 

BCJM, have you ever tried measuring the pH of your kalk reactor effluent? It should be around 12.5 if it's saturated.

[bbyatv]

Oh ya. I had done the same. Multiple pumps outside pumping fresh air into the sump with air stones. I could not get my pH up. Now with this setup, I can adjust my pH up to 8.5 easy. I keep it where it falls at 8.0 in the morn and 8.3 in the eve.

 

Bruce

 

 

^^I love that picture, and the technical term "2-liter de-gas chamber" (which, by the way, receives less respect in the drawing where it's called a 2-liter soda bottle).

 

The OP noted that he's not getting any change in pH when he aerates tank water overnight using outside air. The implication is that he's already in equilibrium with the ambient CO2 levels.

 

BCJM, have you ever tried measuring the pH of your kalk reactor effluent? It should be around 12.5 if it's saturated.

[Origami]

Oh ya. I had done the same. Multiple pumps outside pumping fresh air into the sump with air stones. I could not get my pH up. Now with this setup, I can adjust my pH up to 8.5 easy. I keep it where it falls at 8.0 in the morn and 8.3 in the eve.

 

Bruce

I had taken his first post to mean that he'd aerated a sample of his tank water overnight with fresh air. Not that he'd tried to aerate the whole tank overnight. If it's the second case and not the first, then it's possible he couldn't blow off enough CO2 the way he was trying it because of all of the other things going on in his tank.

[bcjm]

I have done both. I ran the skimmer with outside air overnight or areaed the water in a small container outside air. Neither case changes the water PH.