Hello. I tried searching the forum for sizing information but not allowed to search.

I have a 12X24 inground concrete pool in Florida. I had an old Posi flow 2 Filter the 50sq. foot model, it broke so i purchased a replacement filter(thinking i was doing something right) and got a Star Clear 50sq foot filter installed.
I am finding that the new filter maybe is too small, maybe the posi flow was a better product, but the problem i have had since i had this installed is that is never really gets the pool clean for long. My latest issue is that Algae has taken over and this filter does not seem to be able to do the job(added algaecide and shock many times, still green). The filter element seems to need cleaning daily. My pressure goes from 24psi to 32psi in about 12 hours and once i hose it out it works again for another 12 hours or so before it climbs up. And obviously when the psi is high it is not flowing much water so the cleaning is diminsihed.

My question: What size filter should i have for a this pool? Sorry for the long explanation but i wanted to explain what i have done. I would have searched but the search is not letting me. Thanks.