Protopalythoa was a genus of encrusting anemones - the past tense is necessary because the genus was collectively merged with the genus Palythoa. Unlike Palythoa, Protopalythoa did not have such a distinct spongy, thick basal tissue - the coenchyme - but usually only a little noticeable one. The difference between Protopalythoa and Zoanthus is that Protopalythoa have more pointed tentacles and their tissues have a sandpaper-like, rough feel as they incorporate sand grains into them. Protopalythoa tend to accumulate the toxin palytoxin, which is also dangerous to aquarists and is produced by dinoflagellates. Palytoxin is one of the most toxic non-protein based organic substances, only maitotoxin is considered more toxic. It is absorbed through mucous membranes and the bloodstream and is found in the secretions and body fluids of encrusting anemones - so you can protect yourself by wearing gloves, especially if you have injured skin. Since the Protopalythoa can also spit or eject water as a fine stream, one should also consider eye protection when handling them roughly. In general, the animals are especially dangerous if they are mechanically injured, for example by fragmentation. In extreme population densities, the toxin can also enter the aquarium water and then be dispersed as an aerosol via the skimmer; boiling of decorative objects also produces toxic water vapor. Symptoms vary from nausea and vomiting to chills or muscle paralysis. Native Hawaiians also used palytoxin as an arrow poison in the past. However, no deaths from Zoanthids have been reported to date. The unpleasant thing about Protopalythoa is that they can multiply quickly and thus proliferate - therefore it is best to place them away from the reef structure, because in the end you can only dispose of infested rocks due to their toxicity.
The water conditions are rather unimportant, with high nutrients they grow particularly well, light can be tolerated up to approx. 100-120 PAR and thus quite much. Those sea mats or Zoantharia, which are often called "Paly", do not belong to Protopalythoa, but are Zoanthus with large polyps. In general, many Protopalythoa are ugly and brown-green. But there are a number of interesting color forms like "Nuclear Death" or "Purple Death", or even (Proto)Palythoa grandis, which are nevertheless popular.