Falling back on my engineering knowledge due to my lack of pool knowledge...

You will need to find out what the flow rate is on your pump and check it against your filter. In this case your filter has an effective filter area of 1.7 ft2 and a filtration rate of 20 gpm per ft2. Little basic math should translate that to the filter being able to handle 34 gpm.

Considering that your pump is 1 1/2 HP - you are probably looking at somewhere between 75 and 100 gpm flow on the pump (depending on head and line loss...though the end result will be the same). The end result is that either your filter is too small or your pump is too big.

Now it starts to get a bit fuzzy on my experience with pools... As I understand it, you want to filter your whole pool once every 8-10 hours. So, your pump is close to being the right sized (if my assumptions are correct), however your filter seems to be about half the size it should be.

That results in the water being forced through the sand bed too fast, and when it moves too fast things like algae just get shredded by the sand and ejected back out into the pool as opposed to remaining in the filter where they can be removed by backwashing the filter. And that can mean that while you manage to kill the algae, the dead particles remain floating about in the pool until you manage to sort out the filtration of those solids from the pool itself.