The media is washed gravel. The ph was around 6 before I started and I did add a lot of water to the system. Since I changed the system to CHOP2 I added a 50 gallon sump and the three grow beds probably hold another 10 - 15 gallons each so that is quite an addition to the 550 gallons already in the fish tanks. Almost 20% more water. The water is from the tap and the PH is most of the time neutral. I'm guessing it is the gravel. The last time I added gravel the PH did not change but this is a different batch. The PH I can change, my main concern was the nitrates. Is 60 ppm too high or should I expect that with the amount of fish I have(150 goldies)?