Acid needs to be added when freshwater like rain fills up the pool, and algaecide is added when you have a green algal outbreak. However, it's chlorine that stops your pool from going green in the first place.
I had this problem and got it cleared up but I was doing a couple of things wrong.
Firstly, I didn't use the flocculent. I put some in then vacuumed the following day and it does seem to really help remove the cloudiness. I can see the bottom of the pool again.
Secondly, I read on the flocculent bottle that it's really important to vacuum to waste. The algaecide bottle didn't mention this, which it probably should. I suspect that as I've just been vacuuming into the filter and then backwashing, I haven't been getting rid of the dead algae from the system and that was why it was dragging on. Lesson learned.
After some more troubles, I used an algaecide that said it was specially developed for salt water pools, as well as a salt water branded clarifier. Will be sticking with them in future and hoping the problem doesn't reappear. - Joker
Test for algae by running fingers around under the water against the walls of your skimmer box. If it is a tad slippery or slimy it is algae if not it is pollen. The pollen solution? Add a polymer based clarifier and filter the pool for 8 hours or more (overnight) and then backwash the filter. Pool water should be clear once more… if improved but not perfect repeat one more time.
If this fails to clear up the water then use a flocculent. Lo Chlor Maxi Floc is a good one. Add the flocc and put the filter on to recirculate (don't use filter setting) overnight with the pump turning off at maybe 5am in the morning. There will be a lot of drop out cloudy type residue on the bottom of the pool. Use your pool vacuum to remove to waste not back into filter or it will simply return back to the pool. Water should be clear again.
If not then check the filter medium and change it preferably to recycled glass. If still (unusual but happens) having the same issues you are probably looking at replacing the filter.
Follow the rule of 5. Cloudy pool...1 balance 2 oxidize 3 clarify (first 3 fix 95% of issues) 4 flocculent 5 filter. Nothing outside of these 5 fixes. They descend as they do/don't fix the issue… move through them in order and enjoy the pool. - India77
When you've got the algaecide covered, this video also recommends using a pH neutraliser, super shock chlorine and flocculent to fix your green pool. - Jackson