If you think your pH is dropping there are a few things you can try. First, point your powerhead more towards the surface and get a nice rippling affect going. That will promote better gas exchange. Another thing that can cause low pH is too much co2 in the air in your house. If possible, crack open a window close to the tank and let some fresh outside air in. You can test if you have too much co2 in your house by first testing the pH of your water in the house. Then take a sample of your water outside and let it sit out there for a while with an airstone in it bubbling fresh outside air and then test it. If the pH is higher outside you have high co2 inside the house.
Any buffer that claims to keep your pH at a constant level (like 8.3) contains a high amount of borate. Too much borate can affect the reading on some pH test kits. If your pH is anywhere between 7.8 and 8.3 your fine and it's nothing to worry about. Don't get too caught up in trying to keep it at a certain level. It will always be lower in the morning after your lights were off all night and rise thru the day once your lights are on.
If you KNOW it's low, take 2 1/4 cups of Arm & Hammer baking soda, put it on a cookie tray and bake it in the over for 1 hour. After it cools, mix that in a 1 gal jug with RO water. Dosing this solution will raise your pH, but it will also raise your alk so keep on eye on your alk.
