my PH level has been on the rise recently and is now peaking at about 8.6 at the end of the light cycle.

i currently dose Brightwell Code B for Alk, twice a day with my top off water, once in the morning before work and once in the evening after work. i try to keep it at about 9.0 dKH. calcium is fairly stable in the high 400's, only dropping slightly between weekly water changes, i do not dose the Code A for calcium.

i run a skimmer 24/7 and have some cheato on the same light cycle as the main lamp.

i monitor the PH with a pinpoint probe connected to my RK2. i thought it was just off so i re-calibrated and the readings didnt change. the little API test tube test also shows it to be a bit high at around 8.4 (the dropper test always ran .1 or so less than the probe.)

PH use to read about 8.2-8.3.

suggestions?

i had a high pH problem a little while back and what helped even it out for me was adjusting a powerhead to get a lot more surface agitation. also you should possibly consider running your chaeto light on a reverse cycle from the tank to keep it a little more stable. here are some problems other people have had

High pH

You have to dose alk twice a way to stay around 9 dKH? What is your Mg?

i do twice a day to even out the dose, thought it would be better than all at once. i do about 2ml twice a day. is that a lot?

Mag is at about 1200.

2 mL isn't that much. I have to dose 7-15 mL every day. You could bring that Mg up a bit to 1350 ppm.

What's your before-light pH?

hard to say exactly as the lights come on mid day while i am not home. on the weekends i have spotted it at low 8.3's, it could possibly dip lower to the high 8.2's.

just tested my new batch of water i mixed last night, 8.41.

should i invest in a new probe? its about a year old?

You said you just calibrated the probe, right? Is it still reading the calibration solutions correctly? If so, you don't need a new probe.

I'm having similar. I was sweating it but told not to worry as long as alk and Ca are in check. I've peaked at 8.54 by day recently, and usually around 8.1 - 8.2 by night. I do notice that the more people are in the house in the day, then the lower the pH goes, hence C02 transfer into the water...

If this helps you out any, I tested my alk the other night and it's at 5.44 dKH. Quite low to say the least. So my notion that high pH means alk is inline, was incorrect. Check your alk level ASAP as you probably have low alk too and will need to bring it up to optimum levels.