What causes algae in pool water?
The unfortunate truth is that algae is always growing in your pool water. If your pool is starting to turn green, or if you don’t ever want your pool to turn green again, you’ve come to the right place. One of the best ways to manage the overall health of your pool is by working to prevent algae from forming in the first place. Simply maintain sufficient free chlorine (FC) levels in your pool at all times to make sure that algae will not grow. Chemicals like algaecides or pool shock are expensive and unnecessary.
How do I prevent algae in pool water?
When your FC level is insufficient, you allow algae to grow faster than your chlorine can kill it. Maintain your FC according to the FC/CYA relationship and avoid dropping below the minimum FC level for your CYA. To do this, we recommend testing your FC level every single day with a recommended test kit. Then add liquid chlorine or run your saltwater chlorine generator as needed to stay well above minimum FC. When your FC level is always sufficient, you make algae outbreaks nearly impossible.
What if it’s too late and my pool is already green? Once you have a serious algae problem, you must commit to fully clearing your pool with the SLAM process. You cannot clear a green pool overnight! Again, algae is constantly growing. If you skip a day before you have gotten rid of it all, it starts growing right back. Skip a couple of days, and any time and chemicals you invested up to that point will be wasted. Carefully follow the SLAM process until you meet the criteria to finish, and you will be rewarded with clean and crystal-clear water.
Should I shock my pool weekly?
If you maintain your FC at the appropriate level for your CYA, there is no need to shock your pool weekly. Pool stores recommend weekly shock so they can sell you more products. Any algae that you might be killing with weekly shock only grew because of insufficient FC. The best offense is a good defense: don’t kill the algae with shock, prevent it from ever growing in the first place! However, if it is already too late and your pool is turning green, follow the SLAM process instead of using shock.
Should I use algaecide?
TFP does not recommend the routine use of algaecides. Algaecides generally contain additives that may produce unwanted side effects. Certain algaecides may contain copper which can stain the pools surface and turn swimmers hair green. When properly maintained, chlorine alone is able to kill algae and bacteria in less than a minute, and so there is no reason to use algaecides routinely.
The one exception to our advice against algaecides is during your pool’s closing. Many TFP members use 60% PolyQuat algaecide during the winter months as part of their closing procedures. PolyQuat is not required but may be helpful for pool owners in colder climates as it can outlast chlorine at freezing temperatures.
