I have a 20 gallon fresh water tank. The ph is testing about 7.6. I added some ph down (by Aquarium Pharmaceuticals). How long does it take to fully permiate the water? I’ve retested a couple of times but it doesn’t seem to be having any effect.It is a new tank, set up four days ago. I just added two small angel fish to help get the bacteria established. Ultimately we want to have two butterfly fish, two more angels, three or four bala sharks and one beta. I’m trying to optimize the water quality before adding other fish.This tank is really just a warm up for the salt water tank I want to get in the future. But I want to make sure I can monitor/control water quality before making that step.