I have also found that many zoanthids appreciate some organics in the water,basically not overly clean waters like low nutrient SPS tanks. This is not the case with many but I do know that some of my slower growing types go nuts in dirtier tanks with warmer kelvin lighting...They just do not look that great from all the brown zooxanthellae,give em some time under the blue lights in a cleaner tank and they should color back up in no time. Just a thought,experiments in the coral hobby are a big part of the fun. Let me know if I can "experiment" with one of those speckled fires when you have a spare polyp lying around.