Ph levels in a tropical community tank

Question
we have a 30 gal show tank which we have had for years. Never had a problem controlling our pH and or ammonia except in our betta spawning tanks, which we have adjusted. My question is, since we have moved into our new home, been about 3 months now and have had  our 30 gallon cu=cycling since, we have a variety of tropical, some black veil angle, Mollies, guppies, swords, neons and for some reason we can not maintain our pH level it constantly drops below 6 almost every other day despite us using a pH enhanced and that doesn't even seem to work. I have read and heard so much about using crushed coral to asbilize  your pH but can seems to find the quantity to use per gallon. I was wondering if you could enlighten us as how to maintain the PH. We have gotten into tropical fish in order to keep my dying partner active and this PH level thing has him and I totally stumped, as being a aquarium hobbyist myself, I have nver come along with a pH so hard to stablize.
Sincerely yours,
Bettabob

Answer
hi Bob:  The ratio is one pound of coral gravel per ten gallons of water... but you should apply it in 1 cup or so amount and then wait 24 hours to test your pH.  You do not  want the pH to rise so quickly that it damages your fish.  Do you have driftwood or something like that in your tank?  There are many factors that affect pH.  Some of those would be live plants, plant debris, bog wood, driftwood, peat moss, and peat pellets, peat extract such as black water treatment, etc.  Also temperature, oxygen and phosphate will affect pH as well.  Let me know... dave