Sand Filter does not backwash solids

[Schmo]

Hello everyone. I have a new this year RX Clear sand filter system, 12" filter that came with a 1/2 HP pump.

I am having issues getting solids/waste to back flush properly. After running the first few weeks of the season and frequently back flushing (at least twice a week) the sand filter developed a scum/solids layer on top of the sand that was restricting flow and raised system pressure significantly. After cleaning this out pressures returned to normal.
I setup the filter based on the manufacturers recommendation of about 75 lbs of sand.

I removed roughly 10 to 15 lbs of sand after this issue thinking there may be too much sand for this little pump to properly agitate and clean during the back flushing. The following month or so of use and back flushing I see the pressure is consistently rising even after back flushing. I am debating removing more sand, but I am also wondering if this pump is simply too small for this filter. There is plenty of water flow during the back flush and even running it for 2+ minutes yields no different results.

Any thoughts would be helpful.

[Denniswiseman]

I would be inclined to put the correct amount of sand back in the filter
That "Scum" is probably sun screen or other body application that has been introduced into the pool

[Schmo]

We don't really use sunscreen, very rarely. I do use algaecide, but I thought that was the whole point of backwashing, to clean that stuff out of the sand.

[Denniswiseman]

A properly sanitised pool doesn't need algaecide
Have you used Floc as that will bung up your filter
Normally pumps are matched to the filter as excessive flow through a filter doesn't filter properly
Let's have your numbers (CYA is very important) Use a pool store if you don't have a FAS/DPD kit
FC:
TC:
pH:
TA:
CH:
CYA: