What is the safe upper limit of PH

[arking_mark]

Take your readings with a grain of salt. Most pH probes are only accurate to about +/-0.2 in my opinion and most don't publish their accuracy. GHL claims +/-0.1 accuracy, but this may only be true in ideal laboratory conditions with a freshly professionally calibrated probe.

 

[Miami Reef]

Take your readings with a grain of salt.

Was the pun intended?

 

[GAMGAM]

Take your readings with a grain of salt. Most pH probes are only accurate to about +/-0.2 in my opinion and most don't publish their accuracy. GHL claims +/-0.1 accuracy, but this may only be true in ideal laboratory conditions with a freshly professionally calibrated probe.

True, but +- means it could be actually higher then it says. I calibrated the probe with fresh liquid so it should be pretty close.

I did like the pun. Lol

 

[GAMGAM]

I do not know if your pH is accurate, but if it is, more aeration with normal or higher CO2 air will reduce it.

The primary "risk" from elevated pH is increased precipitation of calcium carbonate on sand (hardening it), and on pumps, heaters, and anything else warm.

Some photosynthetic organisms, such as some macroalgae, use CO2 and those may suffer if pH is too high. I discuss that issue here:

Photosynthesis and the Reef Aquarium, Part I: Carbon Sources by Randy Holmes-Farley - Reefkeeping.com


Relative rates of photosynthesis in seawater (measured by oxygen evolution) at pH 8.7 relative to pH 8.0. A value of 100 means that the rates were the same, and values below 100 indicate less photosynthesis at pH 8.7.

​

​ Species of macroalgae: Relative photosynthesis at pH 8.7 compared to pH 8.1 (as a %):​ Chaetomorpha aerea 75​ Cladophora rupestris 100​ Enteromorpha compressa 67​ Ulva rigida 100​ Codium fragile 76​ Asparagopsis armata 45​ Gelidium pusillum 33​ Gelidium sesquipedale 18​ Gymnogongrus sp. 39​ Osmunda pinnatifida 46​ Porphyra leucosticta 110​ Fucus spiralis 86​ Colpomenia sinuosa 100​ Dictyota dichotoma 53​ Cystoseira tamariscifolia 57​ Padina pavonia 53​

Thanks for the reply Randy, that was an interesting article. Do we know much about the upper PH limit of some of the more common corals we keep (acropora, euphillia, gonipora).

you were right. My probe was reading about 0.15 high so i was only around 8.6- 8.65 at the peak (which is probably perfect) and not really in the danger zone.

I’ve had a hard time finding people who have had negative outcomes from intentionally and carefully increasing their PH (with an acceptable alk). I’ve heard of high PH “events” doing damage (say a kalk overdose) but never someone who was carefully pushing the edge, maybe that’s what Sean was alluding to is that you just can’t physically get it up their safely, and more importantly is there any benefit to doing so.

 

[Randy Holmes-Farley]

Thanks for the reply Randy, that was an interesting article. Do we know much about the upper PH limit of some of the more common corals we keep (acropora, euphillia, gonipora).

you were right. My probe was reading about 0.15 high so i was only around 8.6- 8.65 at the peak (which is probably perfect) and not really in the danger zone.

I’ve had a hard time finding people who have had negative outcomes from intentionally and carefully increasing their PH (with an acceptable alk). I’ve heard of high PH “events” doing damage (say a kalk overdose) but never someone who was carefully pushing the edge, maybe that’s what Sean was alluding to is that you just can’t physically get it up their safely, and more importantly is there any benefit to doing so.

The only thing I recall seeing studied in corals as a function of pH is calcification rate, not photosynthesis.

Reports of precipitation events (excessive demand for alk and calcium) are very common, and stopping pH boosting procedures (such as a CO2 scrubber, kalkwasser, etc.) are among the main things I recommend.

Here's a typical post of mine:

Once a calcium carbonate precipitation event is initiated (due to high alk and pH, for example), you need to break the cycle because the surfaces of any precipitate act as good seed crystals for more precipitation until something gets onto those surfaces and blocks further precipitation.

Here's my generic advice for such scenarios:

1. Stop all efforts to boost pH.
2. Stop dosing alk for a bit and let it decline.
3. Reduce pH by switching to a low pH alk mix like sodium bicarbonate, or a calcium organic such as Tropic Marin All for Reef.
4. Ensure magnesium is normal to high.
5. Keep organics and phosphate on the high side.

After a few days of not dosing alk, restart slowly, adding additives to a very high flow area so it mixes in fast.

 

[arking_mark]

Was the pun intended?

Of course.

 

[djf91]

Can you link the pH probe on here? Based off your first picture I think I have the same unit as you. Not only do these probes go out of calibration quickly but the probes themselves also go bad. If you have the same one I have. Mine currently reads 8.8, but when I first set it up it read 8.3. How long have you been using it for?

 

[GAMGAM]

It’s one off Amazon. had it for a couple of months but seems ok. ill calibrate it more frequently going forward.

 

[Sushi.Reef]

How much is your ph dip over night ?

As low as 8.3

 

[((FORDTECH))]

As low as 8.3

Ok thanks. This is exactly what I am experiencing. 8.6-8.3 daily swing at max.

 

[David_CO]

I travel alot for work so my house is regularly closed up for about a week at a time. after 3-4 days my PH seems to hit a "cap" at 8.55...it has consistently flatlined there as a max for the past 6 months when im gone.

 

[GAMGAM]

Mine is back to the 8.2-8.5 it was before. Can’t be too upset with that.