Need quick advice-Ph Drop

Lisa Cain · Mar 16, 2018

I had a big Xenia in the tank and it died last night. I tested the water and I noticed a big Ph drop from 8.0 to between 7.4 nd 7.8. I removed the dead coral. The stores will not open until 11:00. Normally I keep water but I used it last night. Should I put in a touch of backing soda until I can get some water?

KMench · Mar 16, 2018

Baking soda would actually lower the pH of the tank briefly, not raise it. If you had kalk, that could raise the pH. Otherwise provide some aeration of the water. I would say that drop isn’t awful if it’s closer to the 7.8. My tank runs around 7.8 normally in the winter. Ideally you want to keep swings below 0.2 pH.

Lisa Cain · Mar 16, 2018

KMench said:
Baking soda would actually lower the pH of the tank briefly, not raise it. If you had kalk, that could raise the pH. Otherwise provide some aeration of the water. I would say that drop isn’t awful if it’s closer to the 7.8. My tank runs around 7.8 normally in the winter. Ideally you want to keep swings below 0.2 pH.

Therefore, it is safe to wait until I can replace the water around 4:00 because I ahve to go towork.

Lisa Cain · Mar 16, 2018

KMench said:
Baking soda would actually lower the pH of the tank briefly, not raise it. If you had kalk, that could raise the pH. Otherwise provide some aeration of the water. I would say that drop isn’t awful if it’s closer to the 7.8. My tank runs around 7.8 normally in the winter. Ideally you want to keep swings below 0.2 pH.

This has been a week, first my anenome got sick and is coming back and now the huge Xenia like plant died.

Lisa Cain · Mar 16, 2018

KMench said:
Baking soda would actually lower the pH of the tank briefly, not raise it. If you had kalk, that could raise the pH. Otherwise provide some aeration of the water. I would say that drop isn’t awful if it’s closer to the 7.8. My tank runs around 7.8 normally in the winter. Ideally you want to keep swings below 0.2 pH.

Thank You!

ihavecrabs · Mar 16, 2018

Hi Lisa,

I do not think pH would be the cause of your Xenia death. I had typically always had lower pH 7.7-7.8 in my tanks and I had waving hand xenia for the longest time. I had so much of it that when it tried to escape its rock, I used to clip it and sell it back to the LFS. Half the time, they melted in their tanks.

How long did you have the Xenia for?

Also, do you test other parameters?

Brew12 · Mar 16, 2018

If at all possible, increase air exchange. That should help raise your pH.

Lisa Cain · Mar 17, 2018

ihavecrabs said:
Hi Lisa,

I do not think pH would be the cause of your Xenia death. I had typically always had lower pH 7.7-7.8 in my tanks and I had waving hand xenia for the longest time. I had so much of it that when it tried to escape its rock, I used to clip it and sell it back to the LFS. Half the time, they melted in their tanks.

How long did you have the Xenia for?

Also, do you test other parameters?

Hello I think what killed the Xenia is that I tried to trim it about. I think that it dropped the pH. thank you so much for your assistance.

TinyChocobo · Mar 17, 2018

The PH of your water really has nothing to do with trimming a coral. It's actually fairly normal for the PH to 'swing' from as high as 8.2 to as low as 7.8 and back over a 24 hour period although you obviously want to try to keep it as stable as you can.

PH is a measure of the acidity or alkalinity of your water - with anything below 7 being acidic and anything over 7 being alkaline.

Your PH can be low due to a high concentration of carbon dioxide [carbonic acid] - which is why it's advised to aerate the water to bring the PH up. That said - if the building/room that houses the tank is high in CO2 [say it's sealed up really well] then aerating the water won't help as much if at all.

I have never seen sodium bicarbonate drop PH - but when I used it I would add 1 teaspoon [not heaping, a level even teaspoon] to 5 gallons of water when doing a water change. I would do a gallon at a time over the course of a day or two [you don't want a huge swing in PH, and I was working with a 29 Gallon system].

Sodium bicarbonate is a PH Buffer - it will raise the alkalinity of the water thereby raising the PH. Another way of thinking about it is that bases and acids of the same concentration and amount will 'cancel' each other out - by adding a base [sodium bicarbonate] you will effectively be cancelling out some of the acidity in the water thereby raising the PH.

I am really not convinced that a PH swing is why your Xenia died - not unless you did something that would alter PH in some major way. Let's say that your coral did die and released ammonia - ammonia is actually a bit alkaline and would, in theory, actually raise your PH a little.

I'd say trying to trim/cut on it was likely why it died.

Randy Holmes-Farley · Mar 17, 2018

Sodium bicarbonate will lower pH when first added. Sodium carbonate will raise it, as will hydroxide additives. But none of these should be added unless you need alkalinity.

In general, higher alk will lead to higher pH, but you do not want to push alk too high.

I suspect your pH measurement is likely in error at pH 7.4. At that pH, the rock and sand would be dissolving.

I’d look for other explanations for Xenia problems and ignore pH for a while.

TinyChocobo · Mar 17, 2018

Randy Holmes-Farley said:
Sodium bicarbonate will lower pH when first added. Sodium carbonate will raise it, as will hydroxide additives. But none of these should be added unless you need alkalinity.

I've never seen that happen personally, but to be clear I'm not disputing what you're saying. I always added it very slowly in dilution with a water change - so perhaps it was just gradual enough that I didn't notice any quick drops or raises?

Randy Holmes-Farley said:
I suspect your pH measurement is likely in error at pH 7.4. At that pH, the rock and sand would be dissolving.

Why would that be the case? 7.4 is still alkaline - would it be dissolving just from the standpoint of the PH of the rock and and itself, if you could measure it, being higher than that of the water?

Randy Holmes-Farley said:
I’d look for other explanations for Xenia problems and ignore pH for a while.

I agree with this.

Randy Holmes-Farley · Mar 17, 2018

TinyChocobo said:
I've never seen that happen personally, but to be clear I'm not disputing what you're saying. I always added it very slowly in dilution with a water change - so perhaps it was just gradual enough that I didn't notice any quick drops or raises?

Why would that be the case? 7.4 is still alkaline - would it be dissolving just from the standpoint of the PH of the rock and and itself, if you could measure it, being higher than that of the water?

I agree with this.

It chemically must lower pH when added. The effect is small (about 0.04 pH units for 1.4 dKH added), but it is easy to show mathematically. In words, you are adding only the acid half of the bicarbonate/carbonate buffer system. Carbonate will raise pH by about 0.35 pH units per 1.4 dKH added, and hydroxide boosts about twice that much (0.7 dKH).

If you aerate then to equilibrium with normal air, all of these end up with the same pH rise, about 0.12 pH units per 1.4 dKH added. The effect is more at lower starting alk and lower pH, and less at higher starting alk and pH.

I show the measurements and rationale here:

https://www.advancedaquarist.com/2002/5/chemistry

Randy Holmes-Farley · Mar 17, 2018

TinyChocobo said:
Why would that be the case? 7.4 is still alkaline - would it be dissolving just from the standpoint of the PH of the rock and and itself, if you could measure it, being higher than that of the water?

What matters to the dissolution of calcium carbonate is that the carbonate concentration times the calcium concentration be below a certain value. Normal seawater at pH 8.2 is above that value, but if you lower the pH to 7.7, the carbonate concentration declines as it is converted into bicarbonate. The rock can then dissolve to add more calcium and carbonate into the water until that solubility product value is attained again.

TinyChocobo · Mar 17, 2018

Makes sense - I more than likely was not paying that close attention as my goal was to do it over a few days or a week - so I wasn't adding it and then immediately looking at PH to see a change

. Thank you for elaborating, I appreciate it.