Can Ph be too high and what is the number in which it becomes a problem?

[GARRIGA]

Magnesium bible;

Aquarium Chemistry: Magnesium In Reef Aquaria

This article details the nature of magnesium in seawater, how it is added, measured, and removed from marine aquaria, and how it impacts the maintenance of calcium and alkalinity.

reefs.com

Good article and this was what I was looking for and my primitive chemistry mind then assumes higher magnesium within limits other organisms can survive would reduce the ability of calcium precipitation at higher pH. I think

“More interestingly, the magnesium levels were found to have a very large impact on the rate of precipitation. In batches with no magnesium, and at natural calcium and elevated carbonate levels, calcium carbonate was found to precipitate in minutes. With a natural seawater level of magnesium added to that mix, the precipitation was delayed to 13 to 20 hours. With double the natural magnesium concentration, the precipitation was delayed to 22 to 29 hours.”

 

[DanyL]

Yes. Many organics, phosphate and magnesium all help. Sodium polyacrylate stopped it entirely in my nontank tests until supersaturation got so high it crashed out all over.

Is it the presence of Magnesium in the correct ratios to Alk/Ca that would help preventing it from precipitating, or would excess of Magnesium have any affect on this as well?

Edit: Never mind - the quote from above answered my question. Thanks!

 

[Randy Holmes-Farley]

Is it the presence of Magnesium in the correct ratios to Alk/Ca that would help preventing it from precipitating, or would excess of Magnesium have any affect on this as well?

Edit: Never mind - the quote from above answered my question. Thanks!

Just expanding on it, these things reduce precipitation by getting onto bare calcium carbonate surfaces, blocking the way for more carbonate and calcium to land. In general, the more of these things in the water, the more on the surfaces and the more effective it is, almost without practical limit (but obviously there are other reasons to limit them). Ratios are unimportant in this context, except relative to one another in determining which of these things is doing the most blocking.

 

[DanyL]

Just expanding on it, these things reduce precipitation by getting onto bare calcium carbonate surfaces, blocking the way for more carbonate and calcium to land. In general, the more of these things in the water, the more on the surfaces and the more effective it is, almost without practical limit (but obviously there are other reasons to limit them). Ratios are unimportant in this context, except relative to one another in determining which of these things is doing the most blocking.

That’s a perfect explanation.
I appreciate it.

From my understanding of it now, it means that it wouldn’t necessarily stop the reaction, but instead it would slow it down.
So at the moment that the levels of the blocking elements decrease, the rate of crystallization would increase.

If that’s the case, this could help fight back an ongoing participation without the need to lower PH, by simply increasing Magnesium for a couple of weeks, giving me more time to scrape off any buildup that I couldn’t access right at the moment (under the return pump for example).

 

[GARRIGA]

My take. Excess magnesium would temporarily slow precipitation when pH exceeded say 8.4 then all would return to normal once pH settled back to normal levels such as 8.3. Therefore slightly elevated magnesium might help those wanting to run elevated pH levels.

Problem lies in getting proper magnesium levels based on hobby grade test kits

 

[vahegan]

I have been dosing sodium hydroxide based two-part for quite a few months now, specifically with the intention to raise my pH. It went up from 7.9-8.2 (when I was dosing sodium carbonate) to current pH 8.52-8.55 at night (I dose the hydroxide only at night) and stays around the same value during the day due to photosynthesis. My corals seem much happier at these higher pH levels: polyp extension in acros is better and growth rate is faster.

When my skimmer pump failed a few weeks ago, I had no skimming for some 10 days until I received a replacement pump. As a result, my pH levels got as high as 8.7-9.2 (!) during this period with the same dosing. I was afraid that this was too high, but I have not seen ANY negative reaction in the tank. In the contrary, polyps were hanging like crazy. I expected an increase of nitrate/phosphate due to lack of skimmer action, however they remained in the same range as I normally see (0.04-0.05ppm PO4, 15-20ppm NO3 using Hanna checkers).

I have not seen precipitation or any other abnormalities during this period of elevated pH. I monitor the pH using GHL Profilux and I calibrate the pH electrode once every 2-3 months (I calibrated immediately when I started seeing high values, to make sure these were no measurement errors). My magnesium level is a bit high, around 1490-1520ppm (based on Hanna checker), I measure it once in three weeks. I dose pretty concentrated sodium hydroxide solution (150 g/l) directly into the tank: when drops hit the water, I see magnesium hydroxide precipitation, but these dissolve back quickly in the current.

I am actually thinking of increasing pH a little more, as I have noticed that corals seemed to like the even higher values. However, I think there is no other way to do this without boosting KH, than by limiting CO2 intake by the skimmer - either by using recirculation, or by using a CO2 scrubber on the intake, and I am currently reluctant to do either of these.

 

[GARRIGA]

Seems that skimmer was drawing in house co2 driving pH down. Thereby dosing of sodium hydroxide exceeded tank needs during lower tank co2. Is that a valid assumption?

Not a chemist but due to high home co2 I’ve become rather educated in room co2

 

[DanyL]

Seems that skimmer was drawing in house co2 driving pH down. Thereby dosing of sodium hydroxide exceeded tank needs during lower tank co2. Is that a valid assumption?

Not a chemist but due to high home co2 I’ve become rather educated in room co2

Yes, that’s a common thing with tanks located in rooms with a high CO2 content.

I observed the same behavior with my bed room frag tank.

 

[GARRIGA]

Yes, that’s a common thing with tanks located in rooms with a high CO2 content.

I observed the same behavior with my bed room frag tank.

Assuming that's the case then once skimmer was off then lesser ph boost alkalinity supplement likely a better choice although of corals are doing fine at higher values then we need to start questioning the assumption NSW levels are required.

 

[Randy Holmes-Farley]

When my skimmer pump failed a few weeks ago, I had no skimming for some 10 days until I received a replacement pump. As a result, my pH levels got as high as 8.7-9.2 (!) during this period with the same dosing. I was afraid that this was too high, but I have not seen ANY negative reaction in the tank. In the contrary, polyps were hanging like crazy. I expected an increase of nitrate/phosphate due to lack of skimmer action, however they remained in the same range as I normally see (0.04-0.05ppm PO4, 15-20ppm NO3 using Hanna checkers).

Yes, I dosed kalkwasser for 20 years.

When I experimented for a few months without a skimmer when a pump failed, my pH also got too high, and makes it clear that skimmer aeration is significant.

 

[vahegan]

Seems that skimmer was drawing in house co2 driving pH down. Thereby dosing of sodium hydroxide exceeded tank needs during lower tank co2. Is that a valid assumption?

Not a chemist but due to high home co2 I’ve become rather educated in room co2

I don't think that CO2 content is particularly high in my house. Only two people live in the apartment and windows are mostly open except in winter. I have an air quality meter which shows CO2 levels usually in 405-409 ppm range (except when I open a bottle of beer - it indicates an alarm within minutes!)

However, the skimmer pushes huge amounts of air through the water. When I made my skimmer some 5 years ago, I measured the air draw and it was around 1200 liters per hour if I recall it correctly. Solubility of CO2 in water is very high, especially when they are mixed so well using a needle wheel: I believe that my skimmer basically acts as a CO2 scrubber for the air, dissolving it in the tank...

At 400 ppm x 1200 liters/h = 0.48 liters of CO2 per hour. In 24 hours, this comes to 11.52 liters, which is equivalent to about 22.6 gram of CO2 per day. This is a lot, and will of course have a significant impact on the tank pH. My tank volume is only 65 gallons.

 

[GARRIGA]

I don't think that CO2 content is particularly high in my house. Only two people live in the apartment and windows are mostly open except in winter. I have an air quality meter which shows CO2 levels usually in 405-409 ppm range (except when I open a bottle of beer - it indicates an alarm within minutes!)

However, the skimmer pushes huge amounts of air through the water. When I made my skimmer some 5 years ago, I measured the air draw and it was around 1200 liters per hour if I recall it correctly. Solubility of CO2 in water is very high, especially when they are mixed so well using a needle wheel: I believe that my skimmer basically acts as a CO2 scrubber for the air, dissolving it in the tank...

At 400 ppm x 1200 liters/h = 0.48 liters of CO2 per hour. In 24 hours, this comes to 11.52 liters, which is equivalent to about 22.6 gram of CO2 per day. This is a lot, and will of course have a significant impact on the tank pH. My tank volume is only 65 gallons.

Based on this my grasp being that the skimmer introduces more co2 into tank water through diffusion regardless what atmospheric co2 levels are then wouldn’t using a skimmer be detrimental to pH since it increases co2 vs expelling it? Why perhaps when others add a scrubber the pH rises because they eliminate introduction of co2.

As if my brain didn’t hurt before.

 

[Randy Holmes-Farley]

Based on this my grasp being that the skimmer introduces more co2 into tank water through diffusion regardless what atmospheric co2 levels are then wouldn’t using a skimmer be detrimental to pH since it increases co2 vs expelling it? Why perhaps when others add a scrubber the pH rises because they eliminate introduction of co2.

As if my brain didn’t hurt before.

Skimmers can raise or lower pH, depending on whether the air going into the skimmer is higher or lower in CO2 than would be in equilibrium with the tank water at its current alk and pH.

In one tank, it may actually raise pH at night and lower it during the day.

 

[GARRIGA]

Skimmers can raise or lower pH, depending on whether the air going into the skimmer is higher or lower in CO2 than would be in equilibrium with the tank water at its current alk and pH.

In one tank, it may actually raise pH at night and lower it during the day.

That was my original point to why the pH was higher post pump failure but seemed to be disqualified based on having low room co2 unless I misunderstood what was said.

 

[vahegan]

That was my original point to why the pH was higher post pump failure but seemed to be disqualified based on having low room co2 unless I misunderstood what was said.

Based on what Randy wrote, this only means that in my case the equilibrium pH value is lower than I am desiring to achieve in my tank.

If I had lots of dissolved CO2/low pH, intensive aeration would have reduced its content resulting in pH increase. This is often the case in freshwater planted tanks: people add CO2 for carbon consumption reasons by the plants, and have to reduce/eliminate aeration to prevent CO2 removal. Tthis is no issue for the fish as plants generate a lot of oxygen (by consuming the carbon from the CO2 molecule through photosynthesys to build the carbonhydrates constituting their body, and releasing the O2).

 

[DanyL]

I think this will always be true for those of us who use high PH additives like kalk and NaOH, simply because we disrupt this equilibrium, making the dissolved CO2 available for consumption, and thus artificially creating a larger difference between the tank and the room surrounding it.

 

[GARRIGA]

Based on what Randy wrote, this only means that in my case the equilibrium pH value is lower than I am desiring to achieve in my tank.

If I had lots of dissolved CO2/low pH, intensive aeration would have reduced its content resulting in pH increase. This is often the case in freshwater planted tanks: people add CO2 for carbon consumption reasons by the plants, and have to reduce/eliminate aeration to prevent CO2 removal. Tthis is no issue for the fish as plants generate a lot of oxygen (by consuming the carbon from the CO2 molecule through photosynthesys to build the carbonhydrates constituting their body, and releasing the O2).

This is what's flying over my head. Equilibrium with room co2 means that if skimmer off and nothing else changed then it must have been drawing in more co2 from room air then present in tank which was due to high pH additive such as using some form of hydroxide. My point being that when you mentioned having low room co2 that contradicts why tank co2 would rise post skimmer off line. Unless a skimmer exaggerates the volume of co2 now in tank because it's drawing in more than the tank can quickly equalize with room air. That would contradict the claims that adding a skimmer helps with gas exchange when it pertains to co2. Simple test to run. Anyone running a skimmer (absent having a co2 scrubber) can turn it off at night and observe their pH. Take readings before turning it off then after.

As for plants and there use of co2 that appears to be the same with corals since daytime pH higher than night due to photosynthesis absent any other changes such as dosing high pH additives at night or running a refugium at night. Meaning that relative to co2 consumption by photosynthesis it behaves the same with FW plants as it does with SW photosynthetic organism where if both ran the same where nothing was added at night they'd behave the same as to removal of co2 during photosynthesis and contribute co2 when not in photosynthesis.

BTW, ran FW plant experiments and proved that in the absence of adding co2 than an over populated tank with fish behaved the same as had I added artificial co2. Why I'm confident reef tanks behave in many respects similar to FW planted tanks. Absent fish, my alkalinity bottomed out because plants forced to use carbonates to obtain carbon and my house then as it is today high in room co2 because of air tight construction and too many people and pets.

So that we are clear. If only change was taking skimmer offline then only plausible explanation for why pH became elevated at night in my understanding of pH equilibrium between room co2 and and tank co2 being room co2 is higher which is the point Randy made and the point I had made prior to your claims that room co2 were low. Unless my point above about skimmers infusing more co2 faster than tank can equalize means they are the main contributor of co2 at night and perhaps might be wise turning them off absent photosynthesis.

My points based on your claims that room co2 not the problem. Shedding some new light to me on what could be causing lower co2 concerns for some reefers who find solace with adding a co2 scrubber. Can't infuse what isn't present. Unless your room co2 monitors aren't accurate.

 

[Randy Holmes-Farley]

At normal CO2 levels (outdoor levels), seawater with an alk of 7 dKH and any pH above 8.25 will drop in pH due to aeration.

At normal CO2 levels (outdoor levels), seawater with an alk of 7 dKH and any pH below 8.1 will rise in pH due to aeration.

 

[GARRIGA]

At normal CO2 levels (outdoor levels), seawater with an alk of 7 dKH and any pH above 8.25 will drop in pH due to aeration.

At normal CO2 levels (outdoor levels), seawater with an alk of 7 dKH and any pH below 8.1 will rise in pH due to aeration.

That's my understanding from when you educated me on atmospheric equalization yet my confusion lies in what was posted below. Don't know how to insert quotes therefore rudimentary cut and paste.

In this specific event as I understand it the pH rose after the skimmer was removed due to pump failure. Only conclusion I can derive being either room co2 was higher than normal outdoor levels or the skimmer through aeration infuses room co2 faster than tank can equalize. Poster confirmed room co2 around 400 ppm which I believe is close to outdoor air. Regardless what actual parameters cause the pH to rise the one sole variable removed was the skimmer. Poster continued to dose hydroxides at night which ultimately appears to be why the pH hit 9. Seems the skimmer was holding that back.

Can skimmers possibly infuse co2 faster than tank would naturally otherwise equalize with room air co2?

Poster's pH while skimming stabilized to around 8.5 day and night then rose at night post skimmer malfunction. All values above the 8.1 value base line. Don't recall seeing what alkalinity although mention of it being higher.

"I have been dosing sodium hydroxide based two-part for quite a few months now, specifically with the intention to raise my pH. It went up from 7.9-8.2 (when I was dosing sodium carbonate) to current pH 8.52-8.55 at night (I dose the hydroxide only at night) and stays around the same value during the day due to photosynthesis. My corals seem much happier at these higher pH levels: polyp extension in acros is better and growth rate is faster.

When my skimmer pump failed a few weeks ago, I had no skimming for some 10 days until I received a replacement pump. As a result, my pH levels got as high as 8.7-9.2"