The suggestion has been made that setting your lights to turn off for an
hour in the middle of the day inhibits algae growth without affecting
plants or fish. Easy to try, easy to reverse, very cheap. We have an
ancistrus catfish so the small amount of algae we have is viewed as
food. If it increases we simply stop the algae wafers for a while.

I already do this hour off in the day thing, might try increasing the
duration, i currently do 5 hours in the morn and 5 hours in the afternoon
with an hour break in the middle, maybe 4.5 hours either side of a 2 hour
break??

Is it worth getting a phosphate test kit?