Welcome to the sixth guide in reef-pi aquarium monitoring project series. In this part, we'll learn how to use reef-pi to monitor aquarium pH. Corals are sensitive to pH, and most tropical corals thrive in pH range of 7.6 to 8.4. Due to the high CO₂ in the indoor air and various other biological factors in the aquariums, maintaining stable pH is one of the main concerns in reef keeping. Stony corals require calcium and alkalinity additives for their skeletal growth. But it is relatively hard to increase alkalinity without decreasing pH. Hence pH is monitored closely and use as an indicator to decide how much calcium and alkalinity supplement is safe. 

For example, Acropora (a type of stony coral ) is one of the most popular coral in the reef keeping community. They are relatively harder to keep due to their strict requirements (precise water chemistry, strong flow, strong light), but once provided with the appropriate environment can grow rapidly and shows a myriad of color morphs. pH monitoring and automated dosing (covered in next guide) are two useful equipment in the husbandry of hard to keep corals such as Acropora.

We are building a simple standalone pH monitor, with only pi zero and pH probe circuit from atlas scientific is used. A small clear case housing is used to mount all the electronics. This build will monitor a reef aquarium water pH continuously. This will allow us to visualize the daily pH cycle and alert when it goes out of range.