low ph! Best buffer??

[jharring]

I have always had a consistently low Ph. Around 7.8. I have a 72 g with a 6" DSB. The DSB has been up and running for about 2 months now. The Tank has been set up for over a year. The buffers I have previously used are Kent marine Superbuffer/DKH and Seachem Marine buffer 8.3. Neither seemed to have any affect on the Ph. All my other parameters that I can check for are ok including Alkalinity. My nitrates are sometimes a little high about 20. I also add 2 Sea-Lab 28 trace element cubes. I do regular water changes and feed fish a small amount once a day. I also have a Live rock rubble filter and over 100 lbs of LR in the tank. Does anybody have any suggestions? I also use RO/DI water.
72g bowfront
20g sumpfugium
1 clown
7 damsels
1 arrow crab
1 dragon wrasse
clean up crew
multiple powerheads
excalibur skimmer

 

[leigh]

can you post what your numbers are for salinity, alkalinity, calcium etc... we can be more help then. also, which salt mix are you using?

 

[jharring]

My salinity is 1.023 and I use Instant ocean. The alkalinity is 180 ppm and the chart says it is ideal. I use two different test kits for my ph and they are both the same. My fish don't seem to be bothered, but I have some button and start pollyps that have never looked very healthy. I've stopped using those buffers because nothing has been happening. Is there a better one?

 

[leigh]

what's your calcium at?
if your numbers are right on you should never need buffer. this is what i'm getting at...i could tell you what buffer i use but i don't know if it's any good because i never need to use it. it's all a balancing act.
-leigh