Low PH

[Homeplate]

I have a 55 gal that I have been running for about almost 9 months. I have been using Aquarium Pharmecuticals tests kit. But lately, I have had drop in PH to about 8. So I decided to purchase a Salifert KH/ALK test and a handheld Hanna PH meter. After I calibrated the PH meter, I have found that the PH was actually about 7.8 and that is after an 8 hour photoperiod. Wanted to see what you guys think next course of action for a noob reefer. Dose Kalk? Here is some more info on the tank.

KH = 9.3 dKH (salifert)
ALK= 3.31 meq/l (salifert)
ph= 7.8 (meter calibrated)
sal= 1.024
temp= 81
HOB Remora skimmer , maxijets: 2x1200 and 1x900
lighting= 2 x actinic, 2x10K, photoperiod 8 hours
water changes = 10% every 2 weeks using RO water
salt = oceanic
livestock= fire goby, yellow tang, 2 clownfish, royal basslet
soft corals= mushrooms, xenia, button polyps, a few zoos

I also have an emporer 400 and one of my powerheads is pointed at the surface for agitation. I do have a glass-top which I have read does hurt gas exchange. Any help is appreciated....

 

[Atari]

I would swap out the glass top for some eggcrate material. It's probably holding in too much CO2 which is causing the pH to stay low.

 

[phases99]

I agree with Atari. Your other params look fine. Kalk can help stabilize your PH when lights are off.

 

[Homeplate]

Thanks for the tips.....
I took a PH reading this morning before the lights come on and the PH was 7.5, yikes. Took another reading late in the photoperiod and it was 7.7......All the animals look fine except for the 1 of the red mushrooms, it has developed a white discoloration on the edge of the shroom. Fish seem okay.

My lighting system of 4 - 65w PC( 2- actinic and 2 - 10K). I am not dosing any chemicals other than some Zooplex and Phytoplex. I have a pretty strict water change regiment( 10%/ 2 weeks).

I also took a calcium reading using a Hagen CA test kit (its the only 1 have, i might purchase a salifert here in the next few days) and resulted as 480ppm.

I also added some egg crate to 1 side of the tank to see if this helps for gas exchange and have added 1 hour to the photoperiod. I will extend this slowly out to 10 hours.