Duncan coral dying

[t1a1c1h]

We have a large-ish (25 or so heads) long tentacled green duncan coral in our mixed reef that has recently gine from being fully open, taking food from a pipette ans growing fast to being almost entirely dead with now only 3 live heads! This has happened over maybe 3 weeks despite our attempts to help with iodine based dips which we have used with good effect on other lps in the past. No signs of injury, not near anything that stings, no coral eating fish or inverts in the tank, nor any infections or pollutants (we are aware of at least). The heads detach from the skeleton then drift off around the tank then melt away. Our tank parameters have fluctuated a bit thanks to a dodgy batch of alk supplement and over dosing of iodine but everything else Is recovering including acros, monti, acans and softies. Are Duncan's particularly sensitive to alk or iodine? Or could it be something else we're not checking? Params are now stable nitrates 10, phos 0, alk 160, ca 400, mg 1250, iodine 'normal', iron 'normal', ph 8.2 temp 24.6, no changes to lighting, flow or position in the tank. TIA.

 

[krs1102]

In my (admittedly limited) experience, Duncans seem to hate change. So, fluctuating parameters could be the cause of these issues. How do the 3 live heads look now?
Your numbers look mostly fine (Ca and Phos could be a little higher), but I would suspect that the bad supplement might have led to these issues.

 

[Uncle99]

What exactly is normal iodine?
I trust you mean iodide?
Over dosing iodine is non forgiving....iodide in the range .03-.06 is the max you can use.
What is dodgy Alk....again an Alk spike is non forgiving..

How long has your DT been running?
How long has the Dunc, been in the tank?

 

[t1a1c1h]

Tank has been running nearly 3 years, duncan been in it for about 9 months. We started dosing salifert natural iodine when a load of plating montiporas sloughed their skin off about a year ago, testing regularly as we know it can be problematic, solved the skin loss issue. Current level is 'normal' on the test kit as opposed to 'low', 'high' or 'very high'. The dosing error came from putting the tubes in the wrong bottles so iodine was dosed at alk rate and vice versa.... fatal error it seems but we're only human at the end of the day and mistakes unfortunately do happen.