pH and Pickling Lime

[TexasState]

I've been dumping about 1/4 to 1/2 teaspoon of pickling lime into my tank each night. It dump it in full dose after I swoosh it around in a cup of cold water. My reef system is around 140 gallons of salt-water.
At 7 A.M. my pH was 7.9

At 8 P.M. (when the tank light is still on) my pH is at 8.1

5 minutes after the light goes off, my pH is at 7.69

How low is to low for pH measurement?

This is a new unit. I did not adjust the tempurate when I calibrate the pH last night. I just adjust the reading dead on to 7 at 10 even the room temp was at 72F.

Should I do any kind of intervention to raise the pH to 8.2?
I have the equipment to do it. But I haven't got around to set up the Kalk to drip slowly at night.

[newtosa]

Vinh,

pH should not be dropping from 8.1 to 7.69 in 5 minutes (I'm sure this is what is bothering you). My suspicion (after seeing your tank and the obvious evidence of decent alkalinity) is that it's not really doing this at all. I have 3 reasons for saying this:
1. CO2 will evolve back and forth from water to room air, depending on pH, temperature, and alkalinity (I'm sure you know this - just re-capping). Your pH is not high enough (nor is your living room saturated with enough CO2) to be pulling that much CO2 from air to water that quickly. Tracy Gray has a recent RC post on an otherwise painfully annoying thread - something about Baking Soda in thread title.
2. Someone smarter than I can do the math, but I'd guess it's staggering what it would take chemically to actually pull 140 gallons from 8.1 to 7.69 given your dKH.
3. Your pH at the end of the night cycle (after nearly every invertebrate in your tank has been adding CO2 to the water all night) is 7.9. This should theoretically be your minimum pH value, assuming a normally cycling tank which you obviously have (C02 cycling, not NH3 cycling).

I can't remember if your sump has a refugium environment running reverse daylight? That could influence what I'm saying above, but it would take an awful lot of macroalgae doing an awful lot of reverse photosynthesis all day long (during the fuge night cycle and the tank day cycle) to cause a minimum pH at 8:05pm that is lower than the "other" minimum pH at 7am.

Sorry for the long note. My advice on topics you asked about:
- I would not trust the pH meter yet.
- I would continue the same regimen using a commercial KW product to isolate the possibility that Mrs. Wage is messing with your pH (only as a test for a week; I use Mrs. Wage long term with no problems; you may have gotten a bad batch).

And some unsolicited advice:
- I would get the drip setup set up. One-time CaOH2 additions can create some chemical situations that would require Craig Bingman to figure out (not really, but definitely out of my depth).

Finally, 2 questions:
1. Are you adding the CaOH2 between lights-out and when your get the 7.69 reading? This might not make sense at first, but you could be kicking off some chemical equations we don't understand here. (I'd guess you would want to add it before lights-on, but I'm not sure how you're doing it.)
2. Are you adding CaCl2 of any kind (Turbo-Calcium or something similar)?

Thanks,
Dean

[TexasState]

Thanks for your input. Chemistry is not a strong point. I have a brand new, two days old Pinpoint pH. Just calibrate it yesterday. I was surprised to see a big dip too.

I don't have a refugium, or reverse lightning. Recently I have light diatom bloom. I'm not sure if the diatom bloom is b/c of the Taihitian Blend, me selling off my Conch(good cleaner,) or my roommate spraying air deodorizer.
Last night, after I see the big drop in pH, I mix up and dump in 1/2 teaspoon of Ball's Pickling Lime, and that raise the pH to 7.76. At 5 A.M. this morning, I put in some more Pickling lime, and pH is at 7.86.

[TexasState]

Like I said b4, I didn't adjust the temp when I calibrate my pH, so the pH should be about .14 higher then the current readings.

[Tim Marvin]

Vinh, my PH monitor has been measuring 8.2 during the day and 8.1 at night, and early morning before the lights come on.

[Bbristow]

This is very similar to the problem I was having. I hate using additives, but I finally broke down and did. I discovered that the Kent Superbuffer did nothing for me. I started using the buffer made by seachem and after one use the PH was good for a few weeks. Then I added it once more and I have been staying steady now for a 4 to 6 weeks. I also drip the limewater.

Are you still having the problem? Have you noticed coraline algae flaking off or degression in coral growth?

From what I have seen in my tank, things will start to look worse within a few days if there is a problem with the PH and Ca. :!:

[TexasState]

My pH is still prettly low.
I went back to my kalk dumping, and the purple corraline algae is growing once again.

The only coral that act ****y is the flowerpot, and the leather.