Concrete is porous and can easily make a great home for algae if left unmaintained. Once algae makes a home in the concrete, it is very difficult to remove. This means that part of your regular maintenance routine should include brushing the entire surface of the pool regularly.
In addition, concrete is alkaline based. This means it will continuously increase the pH of your pool water. Water should be tested regularly, and the proper chemicals should be added to maintain a healthy environment.
Concrete is also incompatible with salt. This means that salt within the pool will slowly erode the finish. It’s not uncommon to need to replaster your concrete pool every ten to fifteen years depending on how much you use it.