Brown algae?? HELP NEW REEFER HERE

So I came home one day to brown stuff everywhere is this bad or good



I'll try to post pics



I have 120 gallon tank 20 gal sump

4 ft Fiji sun 6x54w HO t5 light

Reef octopus NWB200 8" pinwheel in sump skimmer

Instant ocean reef crystals salt mix

100 pounds crush coral sand

110 lbs dry live rock

X2 hydor koralia evolution 1500gph

Hydor koralia smartwave controller

Hydor smart level controller auto top off

HMO-200 finnex heater



2 Ocellaris clownfish

10 scallop hermit crabs

1 cleaner shrimp

3 frags of zoas

1 acid rain green bubble tip anemone



Water specs

salinity-32. 1.023-1.024

Ph 8.0

Ammonia 0

Nitrite 0

Nitrate 5 ppm

Alk 9.8 dkh

Calcium 480

Temp 76-78