i am having hell trying to raise ph to 8.3. ive tried dosing alk to weekly water changes with top quality salt and it seems to want to stay at 8-8.07. ive even put an airstone fed from fresh outside air to keep co2 down. the swing is very minimal it never goes below 7.95. could old sand and rock be keeping it down from years of insufficient alkalinity? the highest i got it was 8.15 when i was dosing alk but once i got the alk to 10.5 dkh i stopped dosing and started weekly water changes. i have no sps just softies and a big sump full of live rock. any ideas?