Low ph in chiclid tank

Question
I have a 75 gallon tank with 1 Oscar, 1 red devil, 1 plecatumus and 1 pacu. For a year now I have constantly had to keep pH up on hand. my tap water is 6.5 and gets lower in the tank. i change about 25% water every 2 weeks. i have read online that adding coral stone to a tank can help keep pH up is that correct? what else can I do if not? I'm spending $15 a month on pH increase a month.

Answer
Hi Aaron;

Coral sand or crushed coral can help raise the pH. Don't use big pieces of coral though. It's much more sharp and rough than freshwater rocks and your fish could injure themselves on it. You have some very messy fish in there that get pretty large so all that waste will cause the pH to stay on the low side. Your tank really needs water changes and gravel vacuumings weekly to help keep it more clean. Along with the water changes, crushed coral may help. Without enough maintenance it would still be hard to keep the pH up and could actually be dangerous. Tanks with a lot of waste tend to have elevated ammonia. A pH above 7.0 causes the ammonia to be much more toxic to the fish. It is good to keep those ammonia levels measured too.

At Your Service;
Chris Robbins