ph problems

[avifoox]

i have a 75 galons reef tank on top i have a 55 galon fresh water
4 weeks ago i had an accident and a lot of the fresh water got into the salt water tank since then i changed water (20%) weekly like i always do all my corals are ded or dieing i had a beautifull coraline algee blue and red now all my rock is bleaching or coverd with green hair algee i add lime water on regular basis but cant get the ph to go more then 7.5 ph please help

[Randy Holmes-Farley]

How are you measuring pH? It may be a testing error.

These articles may help:

Low pH: Causes and Cures
http://reefkeeping.com/issues/2004-09/rhf/index.htm

Measuring pH with a Meter
http://www.advancedaquarist.com/issues/feb2004/chem.htm

A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm