The term 'pool problem' refers to a situation in which a swimming pool is affected by an overgrowth of ALGAE. The two crossword solutions for this term are ALGA (4 letters) and ALGAE (5 letters). ALGAE are a type of aquatic plant that can grow in large numbers, leading to a decrease in water quality and an increase in the amount of chlorine needed to keep the pool clean. ALGAE can also cause skin irritation and other health problems. In order to prevent a pool problem, it is important to regularly test the water and maintain proper chemical levels.