Hello! My pool has been doing great until about a week ago, it started getting green algae... today I scrubbed the pool down (with a broom, I'm waiting on my pool maintenance kit in the mail) and I double shocked it with granular shock. After finding this website I realized how important it is to test water and keep the chlorine levels up. If I go to walmart tonight, are any of the recommended test kits there? What else should I buy? Thanks!