Help with deteriorating coral.

[banana2026]

this coral was fine 5 or so days ago. i haven’t changed anything in the tank other than adding a carbon infused filter pad. which i have removed at the time of these photos.
setup:
two months old
20 gallon long
popbloom light set at 30%
canister filter
purple rock
zoas gsp frilly mushrooms kenya tree and this coral(what is she?)
2 ocelaris clowns
2 hermit crabs several snails.
1 shrimp

parameters
salinity 1.026
alk 11.2
phosphate 0.21
calcium 430
nitrate 5ppm
temp 78

 

[Baldyreef]

this coral was fine 5 or so days ago. i haven’t changed anything in the tank other than adding a carbon infused filter pad. which i have removed at the time of these photos.
setup:
two months old
20 gallon long
popbloom light set at 30%
canister filter
purple rock
zoas gsp frilly mushrooms kenya tree and this coral(what is she?)
2 ocelaris clowns
2 hermit crabs several snails.
1 shrimp

parameters
salinity 1.026
alk 11.2
phosphate 0.21
calcium 430
nitrate 5ppm
temp 78

your phosphates seem to be high
any swings?
what flow is it in?
is it directly under the light or in a higher light spot?
how long have you had it?
as far as identification it is definitely a leather but hard to tell exact type due to its current state, most likely toadstool

 

[The Ugly Phase]

tank too young imo

my phosphate is 0.17 and my corals are doing fine

 

[Mr. Mojo Rising]

Is your popbloom the rl60 or the rl90? I'm just wondering why your running it at only 30%? If it is the RL60, then it should be at 90%-100%, if its the RL90, then I would start it at about 50%. I'm thinking your light is too low. You have a long tank, and I see your coral is in the corner of the tank, many lights advertise a light width of 24", but in reality I find 14"-16" is more realistic, so if the coral is too far to the side of the light, its getting even less light.

Your alk is also on the higher side IMO, any reason to keep it so high?

Can you also advise which test kits you are using?

I cannot tell what kind of coral that is. But the carbon is not the problem, it is just coincidence that the coral closed up at the same time you added the carbon