Is it okay to run low Alkalinity with low pH?

[Brandon McHenry]

Hey guys.
I know that not many people worry about pH, especially if it is in the acceptable range of 7.8-8.5, but I however tend to be concerned about the little things, even if I shouldn't be. However, after reading the pH article by Randy I saw that it said when you have a low pH, you should run a higher alkalinity. I have an SPS tank that I am trying to run ULN and I am keeping my alkalinity centering around 7dkh. My pH reads 7.8 on the Red Sea test kit (no I do not have access to a pH meter right now but Ive done side by side comparisons and I believe that the colorimeter test kits are fairly accurate). I have my skimmer intake running outside and a refugium lit 24/7. I believe the issue to be CO2 related because I have done the aeration test and inside the house drops my pH to 7.4 and outside raises the pH to 8.4. Is this lower end pH that I have of 7.8 going to be troublesome with my alkalinity at 7dkh?

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, my comments in that regard (higher alk when pH is lower) is meant to help hard corals that are stressed by the low pH. But there are quite a few folks that keep tanks in the pH 7.8 range that also have alk in the 7-8 dKH range, and seem to be fine.

It is easy enough to experiment over time and see if higher alkalinity helps your particular tank, but I wouldn't stress over it too much.

 

[Brandon McHenry]

FWIW, my comments in that regard (higher alk when pH is lower) is meant to help hard corals that are stressed by the low pH. But there are quite a few folks that keep tanks in the pH 7.8 range that also have alk in the 7-8 dKH range, and seem to be fine.

It is easy enough to experiment over time and see if higher alkalinity helps your particular tank, but I wouldn't stress over it too much.

Thank you for the quick response! When you say stressed by the low pH, are there physical signs that you are referring to? I know that in lower pH environments it is tougher for hard corals to acquire the ions necessary for calcification and precipitate them into their skeleton. So in that regard I would assume the low pH coupled with the low alkalinity may be stressing them out internally but I have no real indication of outward stress on all but one of my acropora.

Also because of the ULNS that I am running Id rather not raise my alkalinity much higher. If I determine that there is stress being put on my corals, is there anything else I can do that might help combat my low pH?

 

[Randy Holmes-Farley Verified Community Expert]

Not physical signs, just slower skeletal growth at low pH, which I interpret as stress. I've never heard that it makes them any more prone to other problems.

I understand about the ULNS. I've not seen any data on whether the low pH might actually help prevent the burnt tips of high alk in SPS corals, but it might (reason being that if the cause of the burnt tips is skeletal growth faster than tissue growth, then lower pH might slow the skeletal growth and help, although I do not know how far one might need to drop the pH to get this potential benefit, even if there is one).

Anyway, unless you want to be the one to test such an idea by risking higher alk, keeping the alk lower seems reasonable.

 

[Brandon McHenry]

Not physical signs, just slower skeletal growth at low pH, which I interpret as stress. I've never heard that it makes them any more prone to other problems.

I understand about the ULNS. I've not seen any data on whether the low pH might actually help prevent the burnt tips of high alk in SPS corals, but it might (reason being that if the cause of the burnt tips is skeletal growth faster than tissue growth, then lower pH might slow the skeletal growth and help, although I do not know how far one might need to drop the pH to get this potential benefit, even if there is one).

Anyway, unless you want to be the one to test such an idea by risking higher alk, keeping the alk lower seems reasonable.

So the only concern that you see is slower growth?

 

[Randy Holmes-Farley Verified Community Expert]

At low enough pH, coral skeletons will begin to dissolve. What pH that is will depend on the alkalinity, but is something not too far below pH 7.8, which is why I suggest that as a reasonable cut off.

But no, I do not know of other specific problems from low pH aside from slowed calcification.

 

[Brandon McHenry]

At low enough pH, coral skeletons will begin to dissolve. What pH that is will depend on the alkalinity, but is something not too far below pH 7.8, which is why I suggest that as a reasonable cut off.

But no, I do not know of other specific problems from low pH aside from slowed calcification.

Okay I will definitely keep an eye on it as well as my corals. Could kalkwasser be a decent safeguard? I have no experience with it but I do know that it helps combat a low pH.

 

[Randy Holmes-Farley Verified Community Expert]

Limewater as a calcium and alkalinity additive is the best way to raise pH using an additive. I use it.

 

[Brandon McHenry]

Limewater as a calcium and alkalinity additive is the best way to raise pH using an additive. I use it.

Can it be used safely without an ATO unit or reactor?

 

[Randy Holmes-Farley Verified Community Expert]

Yes, you just need to add it slowly. Some folks using dosing pumps and some people use drippers (DIY or commercial).

 

[Brandon McHenry]

Yes, you just need to add it slowly. Some folks using dosing pumps and some people use drippers (DIY or commercial).

I have a spare slot on my dosing pump, could that work? What brand would you suggest for a beginner to kalwasser/lime (I saw in your article that they are a bit different). And most importantly, if I would like to try this than how you I go about figuring out how much I have to dose per day to safely raise my pH and how much to I have to subtract from my current Calcium/Alkalinity regiment?

 

[Randy Holmes-Farley Verified Community Expert]

I have a spare slot on my dosing pump, could that work? What brand would you suggest for a beginner to kalwasser/lime (I saw in your article that they are a bit different). And most importantly, if I would like to try this than how you I go about figuring out how much I have to dose per day to safely raise my pH and how much to I have to subtract from my current Calcium/Alkalinity regiment?

Yes, a dosing pump set to just below your daily evaporation could work very well.

How much of what are you dosing now?

 

[Brandon McHenry]

Yes, a dosing pump set to just below your daily evaporation could work very well.

How much of what are you dosing now?

I am doing 70mL of BRS calcium chloride and 130mL of BRS Soda Ash to maintain my levels at 420ppm calcium and 7.0dkh alkalinity. My evaporation is about 3 gallons daily which I do manually in the morning and evening with RO/DI water.

 

[Randy Holmes-Farley Verified Community Expert]

To replace all of that alkalinity additive would require about 1.5 gallons per day. Many dosing pumps cannot dose that much, but other slow pumps would work fine.

 

[Brandon McHenry]

To replace all of that alkalinity additive would require about 1.5 gallons per day. Many dosing pumps cannot dose that much, but other slow pumps would work fine.

What if I just wanted to supplement it with the kalkwasser just enough to raise my pH? How much would that be?

 

[GainesvilleReef]

The maintainable change in the ph is based on the rate that the kalk is added to the tank vs the rate that the c02 consumed by the kalk is replaced. It can be calculated for them immediate addition but only for the short term since the co2 will be replaced and the ph will drop again.

I dose saturated kalk with a dosing pump and it helps maintain a higher ph. You need to have significant alk consumption for it to be effective. It works better when a tank is more mature.

 

[Brandon McHenry]

The maintainable change in the ph is based on the rate that the kalk is added to the tank vs the rate that the c02 consumed by the kalk is replaced. It can be calculated for them immediate addition but only for the short term since the co2 will be replaced and the ph will drop again.

I dose saturated kalk with a dosing pump and it helps maintain a higher ph. You need to have significant alk consumption for it to be effective. It works better when a tank is more mature.

The tank is about a year and a half old from the last upgrade. Id consider it fairly highly stocked with SPS corals with colonies ranging from 4inches to 12-14 inches on my acros and around 18inches on my monti caps. As stated above I dose 130mL just to keep my alk stable at 7.0 dkh. How much do you dose in what size tank?

 

[Myka]

Brandon, I hope you don't mind me jumping into your thread, as I have a related question. If you do mind, just tell me to go get bent.

At low enough pH, coral skeletons will begin to dissolve. What pH that is will depend on the alkalinity, but is something not too far below pH 7.8, which is why I suggest that as a reasonable cut off.

pH in my tank is usually 7.6-7.7 from day one, and occasionally hits 7.8. The aeration test outside rises pH to 8.0 only. It's a calibrated handheld pH meter. The tank is young (7 months now), and in the early life of the tank I assumed the pH would slowly rise as the tank matured. This hasn't been the case. I'm not seeing skeletons dissolving, but the tank is certainly challenged at this point. My parameters are: Cal 400, Alk 7.0-7.4 dKH, Mg 1250, K 400, NO3 not a whiff (Salifert & Red Sea Pro), PO4 not a whiff (Hanna ULR), Temp 78F, 35 ppt.

I've never been one to be too concerned about pH either, but I'm really considering adding a CO2 scrubber to the skimmer intake. I'm worried to increase alkalinity since the nutrients in the water column are "ultra low". I can't bring outside air in because the air here is way too cold. I am adding 500 mL kalkwasser (1 tsp/gal) per day via doser as the only source for calcium and alkalinity supplementation right now. Should I really try to do something about this?

 

[Randy Holmes-Farley Verified Community Expert]

What if I just wanted to supplement it with the kalkwasser just enough to raise my pH? How much would that be?

There's no easy way to know in advance. It boosts pH twice as much per unit of alkalinity as do carbonate additives, and 1.25% of the tank volume of saturated limewater added instantly will spike pH by 0.6 or so pH units, but the lasting of the effect depends on the extent of aeration.

 

[Randy Holmes-Farley Verified Community Expert]

pH in my tank is usually 7.6-7.7 from day one, and occasionally hits 7.8. The aeration test outside rises pH to 8.0 only. It's a calibrated handheld pH meter. The tank is young (7 months now), and in the early life of the tank I assumed the pH would slowly rise as the tank matured. This hasn't been the case. I'm not seeing skeletons dissolving, but the tank is certainly challenged at this point. My parameters are: Cal 400, Alk 7.0-7.4 dKH, Mg 1250, K 400, NO3 not a whiff (Salifert & Red Sea Pro), PO4 not a whiff (Hanna ULR), Temp 78F, 35 ppt.

I've never been one to be too concerned about pH either, but I'm really considering adding a CO2 scrubber to the skimmer intake. I'm worried to increase alkalinity since the nutrients in the water column are "ultra low". I can't bring outside air in because the air here is way too cold. I am adding 500 mL kalkwasser (1 tsp/gal) per day via doser as the only source for calcium and alkalinity supplementation right now. Should I really try to do something about this?

I think a scrubber could be a fine experiment.

Whether you notice any difference is hard to say.