Please choose the correct ending to complete the given sentence: Home and Garden: [header] How to treat algae in a swimming pool [title] Test and adjust the pool's ph. [step] One of the main causes of algae growing in a pool is if the ph of the water gets too high, because this prevents the chlorine from killing the algae. Collect some water from the pool and test the ph levels with a test kit.

Ending1: If it is too high (too low) and the ph level goes below a certain threshold (like 7.5 to 7.9), you can use a thermometer to test the ph. Pull the water from the tap to monitor the ph. Ending2: This will help to determine if the algae is native to the pool. If you have a ph between 6.0 and 7.0 you will want to visit a lab. Ending3: [substeps] To lower the ph, add some muriatic acid or sodium bisulphate. To increase the ph, add sodium carbonate. Ending4: Set the ph level at one of the following frequencies : [substeps] F5-1.5 [title] Make sure your pool is at least 600c (marine units). [step] This percentage is indicative of algae growth, making it a good idea to maintain your pool's ph.

Answer format: ending1/ending2/ending3/ending4