new GFO stresses sps ???

[Mr Reefer 1690]

I have a 75 gallon mostly sps tank. For the past 14 - 16 months I've used between 10 and 15 tbs of regular gfo from BRS, changed every 4 wks, with no noticeable negative effects.
Mid Dec I changed the GFO, adding 10 tbs of new. The next day I came home to a stressed tank. There was no polyp extension. I took no action. The following day 7-8 of my sps have started to stn. I lost some large encrusted frags that I've had for a few months and suffered major damage to a large green millie, green birds nest and garf bonsai that I've had for a couple years. I did some water changes and things started looking normal again
Due to some small spots of hair algae I've recently been changing out the GFO every 3 - 4 days as I understand that I'm using a smaller than recommended amount.
The past 11 times I've changed out the GFO with no noticeable effects. 4 days ago I changed out the GFO and came home the next day to stressed corals again. I did a 20 gallon water change and things are starting to look better, but are still not back to normal. The bonsai and birdsnest continue to stn.
The only action taken in both instances was changing out the GFO. In both cases the reactor was flushed with 2 gallons of tank water prior to allowing the output to enter the tank. Randy's 2 part via dosing pumps are the only additions to the tank besides regular water changes.
Please help.
Sorry the post is so long

 

[jammoye2]

I've had issues in the past with GFO. It caused the same thing, stn and rtn and my tank is still recovering. I still use GFO but at a much lower than recommended dose.

 

[The Velvet Sea]

I'm curious how your parameters are through these incidences. If you're that good about changing your GFO, it could be possible that you are in the ULNS range for phosphates at least. I've read reports of sps being hyper sensitive to other parameters like alkalinity in such conditions. Then again, it could just be the corals' reaction to GFO (reaction to the media or maybe rapid depletion of phosphates?), I'm just trying to hypothesize on the situation a bit.

 

[Mr Reefer 1690]

kh 8.5 , cal 420 , mag 1400

I know I have at least a little phos as I get a light film on the glass and have a few small patches of hair algae.
How can I change the GFO 11 times with no ill effects and now after the 12th change I'm watching corals die?

thanks

 

[Midnightsun]

Sorry but what is stn and rtn?

 

[smtank]

Sorry but what is stn and rtn?

STN:Slow tissue necrosis. Used to be sudden but that has changed.

RTN: Rapid tissue necrosis.

 

[tmz]

kh 8.5 , cal 420 , mag 1400

I know I have at least a little phos as I get a light film on the glass and have a few small patches of hair algae.
How can I change the GFO 11 times with no ill effects and now after the 12th change I'm watching corals die?

thanks

Lot's of ways. Hard to say without some pre/ post parameters: NO3, PO4, alk,sg

Rapid PO4 depletion in the water column is the most likely,imo. The effects would likely be exacerbated by high alkalinity once the inhibiting effects on calcification from the PO4 are diminished. Alkalinity shifts including downward shifts occasion stn, ime. While the causes of stn are unknown it seems in many accounts and my experience that some change in elements that play in calcification are coincident with stn events.

However, subsequence and/or coincidence don't always mean consequence. Something unrelated to gfo could trigger the stn(eg : excess total organic carbon, flow variations due to coral growth, patogenic microbial activity , high NO3, salinity variations alelopathy, detritus build up, temp variation, nightime hypoxia, and so on)