Gsp issues....

[6lkl6l24]

I have not been having luck with gsp.
Tank is 2 months old, everything in it minus a bit of dry rock I had is pretty much taken from my 220 fowlr that was up for 4yrs after it started a leak so, broke it down and started a 180 fowlr and this 40b, so saw almost no cycle.
Frogspawn is doing good, zoas, and mushrooms.
Iv tried multiple frags from 2 different sorces, moved them in different locations and nothing.
The 1 on the left on the sand bed is about 4 weeks old on the right is 2 weeks both opened for like a day and haven't opened again. 1 on left is actually falling apart.
The one on the rock in the other picture is actually about 6 weeks old and iv pretty much given up on that one.

Any ideas?
ph 8.2
nitrate 0
phosphates 0
calcium 400mg/l
ammonia 0
Salinity is 1.025

 

[Raege]

GSP from my reading are photosynthetic but also absorb nutrients from water column. If your truly zeroed on nitrates and phosphates or darn close perhaps an issue for the gsp. Mine loves a dirty tank and bottoming out on nitrates and phosphates can bring on algae issue
Let’s see what the squad think cause rest of corals look happy
#reefsquad

 

[Auquanut]

I've found GSP to be nearly bulletproof, but I've always kept relatively high NO3 and PO4. Usually around 16-20 nitrate and .05 to .1 phosphate. You might try very slowly raising these levels (not necessarily that high) by increasing feeding and/or bioload.

 

[6lkl6l24]

My levels are usually slightly higher but not much, I did just do a 20% water change 2 days ago.
No sump or skimmer, just hob fuge with macro, canister that gets cleaned bi weekly and 6 relatively medium to large mangroves growing out the top that iv had for a couple years in my 220.

 

[Raege]

Very strange for this coral weed to struggle. If you try getting nutrients up you can also target feed them phyto or other nutrient feeds. How’s the flow? Try moving to a different glow area perhaps Mine love flow and only retract like yours when i handle em or crab gets on it picking for a scrap.

 

[Uncle99]

Nutrients way low for this coral type.
I like the numbers @Aquaunut suggested.
I might think those mangroves are the culprit, they will clear the nutrients corals want to survive.