What is my missing link? Cyano, polyp loss, good parameters?

[Greg5OH]

20g tank 3.5 years old, barebottom for a year.
-ph 8.3
-77f
-8.0 alk
-5-10ppm nitrate
-ZERO phos?? New salifert kit
-450 calc
-1350mg
-1.026 sg
-halo mx80 50%
-1 small crab, 2 snails, 1 maroon clown,

My leptasreas have been losing polyps, candy cane is almost dead(2 head frag, one died 1 barelt hanging on.

Zoa, mushroom, anemone look good
Acan flatish, leposeris hasnt grown in a month.

3 days ago i added another powerhead in, i have 4 in there, theoretical flow 5000gph, but water isnt all that turbulent.

Other than phos being zero, i have a big cuano breakout now, what the heck could be causing the lack of growth in corals?

Normally the nem is size of softball, ticked in those pics due to cleaning glass a bit.

 

[KrisReef]

Do you feed the corals?

 

[Greg5OH]

Yes reef roids spot fed 3x a week

 

[Greg5OH]

Yes reef roids spot fed 3x a week

 

[Dom]

Tell us about your lighting.

 

[Greg5OH]

Halo MX80 running 50% power.
Stock lighting schedule,
blues comes on 7am, ramp up to full power (50% of full power) by 10AM
10 Am-12Pm whites come on, stay on till 4pm, 4-6PM ramp down to only blues,
Moonlight from 8-1030pm

 

[Greg5OH]

Halo MX80 running 50% power.
Stock lighting schedule,
blues comes on 7am, ramp up to full power (50% of full power) by 10AM
10 Am-12Pm whites come on, stay on till 4pm, 4-6PM ramp down to only blues,
Moonlight from 8-1030pm

 

[KrisReef]

Yes reef roids spot fed 3x a week

Get more small fish and feed them diversified food and cut back on Reef-Roids to broadcast feeding 1x/week.
I have found that it is easy to overfeed Reef-Roids with spot feeding. This isn’t a concensus opinion but I think your tank looks a lot like mine did when I first started “feeding” coral directly.
My nitrates and phosphate was also reading low but the algae and nasties were loving the environment while the coral was not.

I’m not sure what small fish you could add but an algae blenny, one of the gobies, a hawk fish song with hermit crabs, arrow crab, anything that you can feed food to raise P and also increase rock picking and algae grazing wouldn’t be the direction I would go.

Gl

 

[Greg5OH]

so you think tank is starving? Is the algea/cyano just sucking up all my phosphates?
I do feed my anemone 1x a week half a cube frozen mysis as well.

 

[KrisReef]

The corals may do better with fish poop than target fed Reef-Roids. Having more grazers and pickers helps with the nasties. If you had a larger tank i would suggest getting a Tang for algae and coral feeding.