How do I lower Ph

[hammy]

My Ph is off the charts and I don't know what is causing it. I am doing my water changes normally. I only run my lights about 5 hours a day, and I am feeding every other day. All my other parameters are o.k. I have a 75 gallon tank with about 80 lbs. of live rock and 6 fish. I am having a hard time keeping up with my red algae and i think it is from the ph. Any help is appreciated.

 

[bang guy]

Have you tried a different test kit?

 

[hammy]

Yes, I have tested it and had my lfs test it. How much should it fluctuate during the day? Also how much will lighting affect it? Should I test with the lights off or on?

 

[thomas712]

You need an avarage. Test in the moring before lights on, then mid day through the photo period, then again during the evening. This should give you an avarage.
What are your tests for alkalinity and calcium? What is your lighting schedual?
You might also have a CO2 problem.