Just installed an inground 28'x14' vinyl in September. We were fortunate for a long swim season and actually got to use our pool for about three weeks before covering for winter! Being cautious I chose to drain down levels and shut off pump after covering which lead to a bit of algae growth by March. Fortunate once again, this was easily cleaned with a soft brush and after adding some salt and stabilizer I have good balance and clear water. Does anyone ever completely shut down their pool here in the south?
For those of us who do not experience long hard freezes, closing a pool is just more work than necessary. Chlorine consumption goes down significantly, so keeping it open isn't a huge deal. As for the algae you had, be careful. Simply adding salt and stabilizer won't resolve an algae issue. We follow the SLAM process (link below). If you ever have a relapse, please see that page. Also be sure to update your signature with all of your pool and equipment info, to include which test kit you are using. Have a nice day.
But once you stick around, read some threads, and understand the TFP Pool School philosophy, it will all make sense. Enjoy! 