Leave the cover on or off ?

[PoolDoc]

You'll grow a lot less with it covered, than with it uncovered.

BUT . . . you need to make sure all algae is dead and that the chlorine has been high for a couple of days BEFORE you cover it. I can't offer much more advice that that; many of the chemicals we recommend here, are not readily available in the UK!

[Anonymous [GDPR] European in the UK]

Thank you
The chlorine level is high so will see when we come back.

[PoolDoc]

Have fun!