The above stands true all the time. pH goes down, your bacteria dies. Balancing pH is not hard. Best thing to use is simple crushed coral. One tablespoon will handle 200 gallons of water forever. Will keep pH close to the 7-7.4 mark all the time. I use just 2 tablespoons in a small mesh bag and drop it in my HOB
. I never have to check pH anymore. If your bacteria dies, you may have an ammonia spike now since your filter can not oxidize it anymore. Now you have to deal with that.