5g going on 17g Tank

[syncro]

Thanks for the detailed reply DCDN. The brown algae has lasted 5 weeks. It started just after the cycle finished (week 3) and has gotten progessively worse. Today is week 8. Hair algae started about 3 weeks ago not too bad but slowly getting bigger. How do you tell if you are feeding enough? My fear is the only way to tell is when animals start dying. I've had one stomatella snail die but I think he went through the powerhead. The nassarius snails appear to be growing.

Ammonia, nitrite and nitrate: 0
pH: 8.2-8.4
Salinity: 31
Temp: 24.3 *C
I haven't tested anything else.

Lights: 12h per day, 10am - 10pm
Food: pinch of cyptopleeze, few mL of phytoplankton every other day
Additives: a few mL of MicroBacter maybe once every two weeks
Water: RO/DI water change roughly 30% every two weeks
No reactors, just a little sponge filter and carbon.

Coral
Green star polyp
Blue cloves
Red plating montipora

Invertibrates
3 tiny nassarius snails
3 dwarf blue legged herbit crabs
1 stomatella snail
3 tiny asterina stars
1 porcelain anemone crab

Fish
none

Should I reduce the photoperiod to say 8hr/day and lower the light so the montipora gets more intensity? I'll also get a phosphate test kit.