Colony death from base up - causes?

[Doubledown]

I have 2 colonies, a Millipora and a Natsuta(sp?), that are dying from the base up.

The branches are fully colored with excellent PE, but the bases are starting to die off and turn white.

I had heard that phosphate could be an issue, any other causes?

Last tests (about 2 weeks ago)
Ca 390
Alk 9.5
Mg 1250

I did not test for PO4 at the time. I have not had any ammonia and last test for Nitrate showed up as minimal. There is around 8000 gph circulation in a 180 so flow shouldn't be an issue.

Any help would be appreciated.

Thanks
Chris

 

[mokujin22]

your numbers look good. even if PO4 is minimal-zero, sometimes corals RTN for no apparent reason whatsoever. how is your flow towards the bottoms? are they positioned such that the bottoms are sheltered from the flow? it doesn't seem like it, but it may be the case.

are the corals RTN'ing or just losing color from being shaded from the branches above? if it is RTN (skin sloughing off, progressing quickly) frag them now at least 1/2 inch above the dead area and throw away the bottoms.

how long has your tank been setup? i assume you have a skimmer.

t.

 

[Carman34L]

check for AEFW, pull the colonies out and look for little egg sacks, tiny brown dots. you will probably need a magnifieing glass.


edit*

millies dont get them so dont check the millie

 

[Cody Ray]

My guess is that because of upward growth the base is being sheltered from both flow and light.

 

[GMGQ]

I've lost 2 colonies this way. Here's a link of one:

http://members.shaw.ca/adina_gary/reefblog/livestock/acropora02_purple_tips.htm

I had that acro since January, and as you can see, I've fragged it. But the frags havent been doing that great either. 3 of the 5 have done the same thing (turned white from the bottom up), and the remaining 2 have turned white at the base too, but the tips are hanging on.....

The other one I just lost after 3-4 days. It was doing fantastic, then POOF, came home one day and 2/3 from the bottom up was white. An hour or two later, the whole thing is gone.

I've got lots of other acros, and they're still doing fine. So I dunno.