How to remove clumps of algae from pool after using algicide
When you added the algaecide it contained a flocing agent which clumps up the dead algae which it then settles to the bottom of the pool.
Filters do not filter out dead algae and all you're doing is recirculating the dead algae.
How to Fix

Some pool owners will need to fill their pool up with water in order to proceed to the next step.  You may not.
The multiport valve on your filter may have a Waste option.  Use it to blow out the dead algae while you vacuum.  Do no use the backwash option, only the Waste is needed.
After you have blown out the dead algae, then you will probably need to tap off your pool again, then backwash and rinse.

If the multiport valve doesn't have a WASTE option, then you will probably need to consider purchasing an external pump and attach it to the vacuum to blow out the dead algae into your garden.