Actually most of the large zoanthids that people call "palys" are Zoanthus gigantus (PE). Some of them are really Palythoa spp. though (not PE).
Zoanthus gigantus are the PE (People Eaters), and they normally have those green lines when they close. They also normally don't have any grain of sand attached to their structure. The skirts are round, most of the time, except when they are under strong current, when they develop a longer, many times pointed, skirt where the current is touching them. Their mouths are also green, like the lines.
Palythoa spp. have a faster reaction to food particles, but that doesn't mean that Zoathus spp. aren't going to feed.
What I suggest is to feed them at night, if they are open. Not all species of Zoanthus open at nigh at all times too, so...
The reason to feed them at night is to avoid the fishes to steal the food from them.
Turn off all the pumps and let the food particle
drop on them.
You don't have to squirt the food on the zoas! They will open their mouths gradually and feed on the particles, if the food is of the zoas' interest!!!
Zoanthids need to be fed food particles according to their size and type.
Best foods are dry coral foods like Reef Roids and Reef Chilli type of foods, and most species of zoas will be happy with them.
More here:
Article on zoanthids feeding behavior.
http://www.reefcentral.com/forums/showthread.php?t=2180156
What was the best additive or food you offer to your zoa tank?
http://www.reefcentral.com/forums/showthread.php?t=1814212
Artificial food study for corals.
http://www.reefcentral.com/forums/showthread.php?t=2167572
Hope that helps!
Have fun!
Grandis.