Sir Patrick sorry about you SPS but did find this. I don't personally keep them so I really have little experience with them.
Genus Parazoanthus: the yellow polyps
There is more than one type of parazoanthan, but the only one you'll see with any regularity is the currently un-named species that used to be called Parazoanthus gracilis, better known as "yellow polyps". For whatever reason, it has been decided that the gracilis is wrong, yet no new name has been given to replace it (yet). Anyway, these are solitary zoanthids, although they do usually form colonies. What I mean is that the individual polyps don't neccessarily stay connected together like sea mat, as connecting tissues may or may not be present, but they typically live close together in groups anyway. Oftentimes they are only joined by thin strips of flesh called stolons, or are found in little patches with there bases growing together.
Yellow polyps have a taller body topped with much longer, thin tentacles that are indeed used for feeding. However, even though the polyps are taller than those of Zoanthus, they are typically smaller in diameter, usually being less than a 1/4 inch across. In addition to being found growing over hard substrates, some parazoanthans are also often found living on other organisms, such as sponges, too. And, while other varieties with other colors are occasionally offered, yellow polyps are, of course, yellow in color (or at least yellow-ish).
Yellow polyps can often thrive under a wider range of lighting conditions than the sea mats, but in general the brighter the lights the better. They are also "softer bodied" and will prefer a lower current, with low to moderate flow being best. They'll also greedily eat small meaty foods you may give by hand, and like so many other creatures, they will benefit from the use of plankton-type foods and/or a D.S.B. set-up, too. But, again, I've also seen them thrive in some aquariums when no food was provided at all.
As is the case with Zoanthus, you do need to be careful with these when it comes to where they are placed, though, as they can also kill other corals they come into contact with. They can multiply quickly under optimal conditions and will sometimes dispatch anything in their path as they spread, so watch out. But, then again, they are often susceptible to stings from more aggressive corals, too.
All in all, yellow polyps can be exceptionally hardy. However, many other parazoanthans you may see at some point may live in association with other organisms, and often rely on those organisms in some way. And unfortunately, these species of Parazoanthus will likely die if the organism they are living upon dies. In other words, if you jump on the opportunity to buy an unusual specimen that consists of some parazoanthans living in/on a sponge and let the sponge die - the polyps will follow suit. So, it's better to stick with other specimens that are less demanding. In addition, note that there are some species of Parazoanthus that are azooxanthellate (can't use light to produce food) and will rely on food. Thus, they would require some form of food, provided regularly, and be much more difficult to care for than other species, as well. These are uncommon in the hobby though.
http://www.saltcorner.com/Articles/Showarticle.php?articleID=54
~Dee~
Good luck with your SPS and hopefully they will recover.
