Do NOT add anything to raise the pH in your system. This almost always leads to issues, especially for those new to the hobby. PH is affected by the CO2
exchange going on in our closed systems. Because of this, it naturally goes up and down as day and night passes.
If one wants to alter the pH in the tank, it is done in two ways. One is to create more water movement at the surface of the tank. CO2
out and oxygen in means higher/more natural pH number. The second is algae. To grow and do their thing, they require light and so on...if one is using an algae type of filtration system like a refugium or algae turf scrubber, running it on an opposite lighting schedule from your display tank will create a stable pH level as the 'day' phase will be going on in this area when the lights go out in your display tank.