Large sps colony dying from the bottom?

[Animal-Chin]

I have a huge birdsnest colony smack dab in the middle of my tank. Its Gotta be 3 years old and has grown from a tiny frag to the monster it is today. So last week I notice some white at the base but didn't think much of it. Now, entire branches are dying off over night. Its happening fast! I've clipped off the dead stuff to try and prevent spreading but anyone know what could cause this weird shift?

Only factor in my tank that's changed is I've pulled 5 fish to reduce bioload and have water changed my tank aggressively for maybe 2 months to bring my nitrates from 10 down to 5. I was changing 20% weekly.

Could it be a pest attacking?

Parameters

Phos - 0
Nitrate - 5
Cal - 450
Alk 10.2
Temp 80

Everything else in the tank, my acros, monti, lps, zoas, everything is totally fine, its just this one big birdsnest...

[rsisvixen]

From what I've read it seems most corals like some nitrate in the tank.

It could just be yours was adapted to your levels and it changed to rapidly for it to deal with once you removed the fish and did the water change.

Or so I suppose

[Animal-Chin]

Ya I agree and I do still have a reading of 5 so there is some in there. I thought at first maybe the reduction was the issue but I reduced the nitrates over 2 months so it wasn't a sudden shock to the system. I have way more sensitive sps coral in the tank that show no sign of stress either, its just this one big coral.

Gonna dip it tonight I guess. I'm also going to buy another alk test kit just in case mine isn't reading correctly.

[d33ps3a]

If it's huge maybe it's no getting enough light in the bottom? Led lights seem to have that problem. T5 lights have more coverage.

[e46er]

When my birds eat got big it was 20"X20X15 atleast when I fragged him it died underneath as well even tho the rest was happy I just chalked it up to wasn't enough lighting getting to the bottom this was under 2 2x250 mh

[04V10]

What d33ps3a said!