Acro STN event help

[jgraz]

I've been experiencing a large scale Acro STN event that I can't seem to put my finger on. Its kind of been progressing for awhile but I can at least trace it back to about 6 weeks or so. I am at a complete loss at this point so any and all assistance is appreicated. This is currently only affecting Acropora. All LPS and other SPS like birdsnest and montis look great with no ill effect. The Acro's have lost some color but other wise have good PE on unaffected areas. Though almost all are receding from base up slowly.
System: 90gal, 40 breeder sump, SWC 160 cone skimmer, TEK 8x54w T5, BRS Dosers for Calcium(55ml per day) and ALK(55ml per day), ECOBAK pellets in a Reef Octopus reactor, 2 MP40's for flow.

Parameters: Salinity- .024
Ammonia/Nitrites-0
Nitrates-0
PO4-.02 on Hanna
Calcium-430 Red sea Kit
Alk-7.2 Red sea Kit

Dosing/Feeding: I feed just about everyday a variety of different food and different days. I dose Zeobak every saturday and Amino's 2 times per week. Cal/Alk are also handled by dosers.

Livestock: 2 O.Clowns, Hippo, Kole, Yellow Tang, Blue spot watchman goby, Melunarus and Sixline Wrasse, Bangaii cardinal, Mandarin, Cleaner shrimp and the usual compliment of Hermits and Snails.

I have done several dips over the last few weeks and no pests have been observed. I have dipped in Bayer and Coral RX during those sessions. I may have seen a slowing of recession after a couple of the dips but it picks back up after a few days. I have fragged a few of the corals above the STN line and remounted on fresh plugs with mixed results. I have also tried to use glue around the STN line but that also failed to halt progression.

Im kind of at a loss here. I have had my testing checked buy another person using their kits and have had comparable results. I have also tested at various times during the day and have seen no significant swings/changes in alk or temps. Thanks in advance

John

[mayjong]

kh is a little low, hows mg?

[jgraz]

Mag is at 1350.
Alk can run low in a UNLS system and Biopellet use drives it down a bit as well

[Allmost]

what exactly do you dose in terms of bacteria and carbon ?

I assume you run bio-pellets, and dose Zeobak ?

when did you add the pellets ? has there been any change in the last couple of weeks to its operation ? like flow, amount or anything else you can think of ?

USUALLY ... STN from base up is result of po4 or nutrients being processed/ removed too fast. At this point, I would advice feeding the tank daily, more food, maybe feed the fish twice a day. this increase in input will take the stress off corals, and hopefully stop the STN.
When STN stops, then you can adjust your removal and introduction of nutrients to make it perfect. [biopellets vs feeding]



Also, meanwhile test KH and CA++ and Salinity daily, to be sure its not drifting. did you notice lower consumption of KH in last couple of weeks when STN is happening ? did KH increase as result ?
its complicated but important to keep KH as stable as possible in these situations. the uptake will change all the time and you will need to be on top of it.

let us know how it goes.

HTH,

[sahin]

kh is a little low, hows mg?

IMO this is fine (7.2).

To be honest, I cannot see anything out of the ordinary. You've already checked for pests etc.

The only two things that can potentially cause an issue that I see is the Biopellets and the Zeobac.

May stop the Zeobac dosing. And as a last resort, I would take the Biopellets off line, if at all possible and see what happens.

[jgraz]

Well someone else asked a question about anything that changed in my system and it made me think back over the last few months. In April and may I went through a bought of AEFW's and was dipping weekly. This ended right around the time I started noticing the STN.

[Allmost]

then your corals are just weak from all the dipping, keep stable, feed more particle food and should recover.

is it the same corals that are STNing now ?

[jgraz]

then your corals are just weak from all the dipping, keep stable, feed more particle food and should recover.

is it the same corals that are STNing now ?

Yep. I was dipping all the acros.

[Allmost]

then stability, more feeding, stay on top of water changes [for elements] and you will be good to go :)

best of luck.

[jgraz]

then stability, more feeding, stay on top of water changes [for elements] and you will be good to go :)

best of luck.

Thanks, will do. fingers crossed