ph out of tap is between 6.4 and 6.8 so is ph in my tank. i have a 75 gallon,sand substrate, 2 fluval 404's and in it are 2 retic stingray pups. ammonia, nitrIte,nitrAte- 0ppm,0ppm,5ppm. Ive been soaking 2 pieces of driftwood about 17" long each. i know driftwood lowers your ph. my question is How can i safely raise my ph to where the driftwood wont lower it to dangerous levels??