Consistently high ph in a new tank startup

[SmokinDaReefer]

Done tons of research and have tried all sorts of things to get my ph down and none of it seems to be working.

Details:
30gal acrylic display w/ 20 gal glass sump
40lbs live sand
roughly 12 lbs live rock(dry)
using Reef crystals for salt
total water volume is roughly 40 gallons

ph has been consistently reading at 9.1 to 9.3, all other params are good, tank is starting to cycle, have a diatom bloom currently.
dkh - 8-10
ammonia - close to 0
nitrate - 16-20

i've added super buffer at the recommended dosage, have also added several times ph down, which works for about 15 minutes and gets the ph to mid 8's, but over the course of an hour, it rises back to 9-9.3. i've done 10 gal, 15 gal, 5 gal and another 10 gal water changes throughout the past couple days, ph drops for an hour or so but rises back up to the 9's by the next day. tested my raw water, shows 7.2, tested the water after i mix the salt and its right on 8-8.2.

Need help. can't figure this one out. was thinking of getting some peat to try and buffer it down, but i don't want to deal with change in water color as well as it staining my sand and rock.

Thanks!

Edit: have 2 other tanks, 1 salt and 1 fresh and both of those have no issues with PH.

 

[Randy Holmes-Farley]

Testing error 100%. The pH is definitely not above 9.

pH is NEVER high enough to be a problem in a reef tank unless you overdose limewater (kalkwasser) or other high pH additives.

 

[Randy Holmes-Farley]

Stop adding anything. The pH down and the buffer just act as opposites to lower and raise the alkalinity.

 

[SmokinDaReefer]

Ok, i'll check out my probe and see if that's where the issue is.
Just as a note though, i've used both the probe on my ReefKeeper as well as API test solution, both showing the same results, but i will verify tonight.

 

[Randy Holmes-Farley]

All I can be sure of is the pH is not above 9. If it were, the tank would be milky white with precipitated calcium carbonate.

 

[SmokinDaReefer]

Ok, thanks for your help! I'll go through my tests again tonight, pull the Ph probe and stick it in test solution that i know the Ph of and see what it says then. Water is crystal clear right now, so if 9 or higher would make it milky, its definitely not.

 

[Randy Holmes-Farley]

Ok, thanks for your help! I'll go through my tests again tonight, pull the Ph probe and stick it in test solution that i know the Ph of and see what it says then. Water is crystal clear right now, so if 9 or higher would make it milky, its definitely not.

I'd recalibrate with fresh pH 7 and 10 solutions.

This has more:

High pH: Causes and Cures
http://reefkeeping.com/issues/2005-03/rhf/