You think I should remove the oyster shells? I have read in many places that is the best thing to raise alkalinity. My tap water replacement is 7.0, I have had to add 30 to 40 gal in the past week because of the evaporation, its been in the mid to high 90's this week. My media is gravel, regular 5G gravel, washed but rough on the edges. My water in the tank is crystal clear and very light fish smell, Iv'e seen indoor tanks smell much worse than my tank.