Corals closing up

[karsumms]

So for the last few days our corals have been closed up and trying to figure out why.. this green algae has started growing over the last week and we noticed this bug-like guy moving tonight. Green algae is also starting to grow on the frag plugs and a greenish brown constantly covering the glass. Is this something that can be causing the corals to close up suddenly? All the fish are doing well besides hippo tang getting ick but is being treated in quarantine. Any suggestions?!! Thank you!

Water temp- 78 F
Salinity- 1.025
Ph- 8.0
Ammonia- 0 ppm
Nitrites- 0 ppm
Nitrates- 0 ppm
Phosphates- 0.25 ppm
Calcium- 420
Carbonate hardness- 196.9 ppm
Magnesium- 1485 ppm

75gal tank with fuval fx6 filter, fuval diy refugium, seaclone protein skimmer, UV sterilizer, ice cap 2k wave maker, 2 AI prime lights and a heater. Started the tank 5 months ago, been cycled for 2 months.

 

[Super Fly]

I'd do few water changes or add a GFO reactor to get the PO4 level below 0.10 but don't reduce PO4 level too quick and see how the tank does. Nuisance algae forming is sign of too much nutrient & poor water quality. I'd stop adding any new livestock to give tank's beneficial bioload time to catch up.