Low pH in SPS System

[DT's_Reef]

My pH in my 120 runs 7.80 in the am to 8.0-8.1 at the end of the light cycle. My pH probe is brand new and calibrated with fresh solutions.

Alkalinity is 9, magnesium is 1500, calcium 450. I use carbon and 40mg O3/hr with an ATB medium cone skimmer.

Tons of in-tank and surface flow. Open rock structure, 1 inch fine sand bed.

Jewel tang, golden angel, flamehawk, 3 small cardinals, and a pair of dragon pipefish.

I use a two-part system, not a calcium reactor, although I do have a kalkreactor dosed by a Liter Meter.

I would think my pH would be higher but no matter what I do, it still ends up the same.

My reef is about 20 feet away from a small kitchen window which is open at all times, so I would not think it was a Co2 issue. I took a cup of tank water at 7.7 and vigorously aerated it with a wisk for 2 minutes outside, detected an increase to 7.8, then it went back down to 7.7 within a few minutes.

Or...is it totally fine to have a 7.7/.8 - 8.0/.1 pH with an SPS system?

[Genetics]

This is a user preference. My pH was running the same as yours. I eventually got tired of it and added a kalkreactor for the night hours. Keeps my pH at 8.2 these days. If you are set on using a two part I would suggest adding a bit more in alkalinity to try to buffer the swing at night. This of course will lower your calcium levels, which may not be ideal for an SPS tank. And your pH will still drop at night. The pH though is not terribly low and so I would recommend not changing anything unless the pH is falling farther than 7.8 at night.

[j.prostrata]

If you can run a hose from your skimmer to fresh air that will also help raise PH. It has worked for me and my ph now runs 7.95-8.15. Used to run 7.7-7.9 before bringing in fresh air.

[SuperNerd]

I think if you want your pH to be higher then maybe you would need to increase the evaporation rate so you can add more kalk topoff at night, when the pH drops? If you do that though it will also increase the alkalinity and calcium.

Or maybe try just dosing your current kalk level at night and see if that alone can keep your pH constant.

Some people have kept SPS systems in the 7.8- 7.9 range.

[DT's_Reef]

My 120g evaporates a bit less than a gallon of water a day, so I believe it's pretty efficient that way.

I can't run a hose from outside given the location of my tank, so that's not an option unfortunately.

My kalkreactor is not running at peak efficiency (the stirrer is busted), so I think I"m going to get a new one and then try to increase the evaporation bit a tad.

[Charlie Davidson]

When my kalk mixer is no running peak-- PH drops to @8
Normal 8.2.. I say fix RX then go from there..
BTW, I have 100% kalk water makeup ...

[aurora]

I'm of the opinion that your pH is just fine.

The last time I checked my pH was 4 years ago and IMO, it is a worthless parameter if your Alk is stable at 9 as you say. If you are chasing a specific pH, you are only asking for trouble. Your parameters are just fine. Don't try to alter them to get to a specific pH. There are multiple stories of tank crashing from white out when people try to do what you are doing. Several factors affects your pH such as CO2 level in your house, how much you skim, how many fish you have, the salt that you use, and even the accuracy of your pH probe. In effect, I would trust my Alk test much more than my pH probe. Anyone who's been reefing for a while will tell you to ignore your pH if your Alkalinity is stable. Do a search on RC for white outs and pH and learn from the mistakes of others.

[moo0o]

i think your pH is fine!

you could try.. a reverse lighting cycle for your macroalgae if you have any.

[DT's_Reef]

Thanks for all the information. I'm wanted to replace my kalkreactor anyway, so if I get one that actually works like it should, perhaps my pH will go up .1 or so.