The pool is too dirty to swim in, Message won't disappear.

Have you had this problem dealt with, I have this problem also, did you buy the pool cleaner? Mine started after I bought and placed the pool cleaner!

No, I have not. I bought multiple pool cleaners and put them in a dirty pool. Then the glitch happened.

I'm getting this problem to. Only way I can get away from page is to close my tablet. But tried clicking on another SIM when I restarted, specifically chose one nowhere never a pool (one at camp ground) and message still came up, meaning all my SIMS are effectively unavailable.

After closing tablet I restarted game, used menu to take me to a different house, one that had a pool. Message came up again but after clicking on it several times it stayed off for lo n g enough for me to click on the pool and send a SIM to clean it. 

Then returned to house where problem started. Clicked on message, it took about eight clicks before I could click on pool and send SIM to clean it. As it was a complex pool, like the one in your screenshot, I then sent a second SIM to clean the other end of it.  In my house there was a second small pool so I bought in a third SIM and using the same repeated clicking method set them to work cleaning the small pool. 

Hope this is of help.