I,ve seen worse, When I decided to breed my pair of clowns a trick to help them start is to overfeed them and let algae grow,my HA was all over my LR
and about an inch to 2" in length.Since they started laying I started the cleanup,
I used a 3/4" hose to remove 30% of tank water,whilst doing this I used the hose to remove as much HA as poss by sucking the HA into the hose then using my finger to block off the hose and pull the HA off the LR
and down the hose, I did this over a 3 week period and cleared most of it and now the water quality,feeding and lighting schedule is doing the rest. Patience is the key as stated before.