Sudden pH Drop

[Ruthie Kansas]

We put the live rock in our tank about 2 months ago. Since that time our pH has been stable (8.4 during the day & 8.2 at night). This morning, we added a clean-up crew to the tank. It consisted of 36 turbo snails (astrea), 6 cerith, 6 nerith, 12 nassarius, 25 hermit crabs, 2 emerald crabs, a sea cucumber, a serpent starfish, and 2 scarlet cleaner shrimp.

Right now, the pH is at 8.05 at a time of the day when it is usually at 8.4. Should I be concerned about this? Is this normal? If so, why does it happen?

In addition, I should mention that yesterday I added sand to the aquarium. However, I didn't notice any substantial change in pH after adding the sand.

[Randy Holmes-Farley]

All of those creatures are consuming organics and releasing CO2, just as you do. So that may be why the pH declined a bit. They are also releasing more ammonia, and the nitrogen cycle, when stopping at nitrate, also reduces pH by producing acid.

I'd just watch it over time and see what happens. You may need to begin to use a high pH alkalinity supplement, like limewater or a high pH two part system.

FWIW, aragonite sand can also cause a one time drop in pH as some carbonate precipitates onto it.

[Ruthie Kansas]

Thanks for the quick reply. We are currently dosing 20 ml/hr of limewater. Should I increase this to try to raise the pH or just wait?

[Randy Holmes-Farley]

Do you know the values for calcium and alkalinity?

Howe big is the tank?

[Ruthie Kansas]

At 1:15 pm today the pH was up to 8.22. The calcium is 470 and alkalinity is 10.1. We have a 55 gal. tank.

[Randy Holmes-Farley]

Those sound perfect. I'd keep on as is. :)

[Ruthie Kansas]

Thank you very much.

[Randy Holmes-Farley]

You're welcome.

Happy reefing. :)

[Ruthie Kansas]

I have one more question. The pH is back to normal now. I understand how adding the snails & crabs lowered the pH through the release of CO2, but what brought the pH back in line?

[Randy Holmes-Farley]

but what brought the pH back in line?

I don't know. Less CO2 in the air around the tank? More limewater? A test that is erroneous? It could be loads of different things. Just be glad that it did. :D