Hi,
Hmm...So, what is your alk ? One thing to note is that kalk additions with vinegar impair alk measurements. Vinegar makes the alk look better than it really is. Low pH can be caused by many problems and the solution is not always obvious -- in other words, high alk may not solve your problem...just delays the problem.
http://www.advancedaquarist.com/issu...e2002/chem.htm
- Victor.