Algae issues are a result of nutrients in the water column.
With 'crazy' algae growth, you won't get an accurate reading on the nitrate/phosphate levels since they are consuming.
How often are you doing water changes? Are you using
ro/
di water? How often and how much are you feeding? Was the tank cycled?
I'll assume your clownfish is stressed due to the parameter issues going on in the system and is showing you that it is ill.
At the end of the day, the answer is large water changes with
ro/
di water. I'd also work on adjusting your skimmer so it is skimming again. During your water changes, manually remove as much algae as possible.