Using my iPhone to take some pics of my aquarium, just before the daylight LEDs go off, and then after when the deep blue Kessil light is all that's illuminating the reef. I managed to capture some of the fluorescence these zoanthids put off under the right light--and by right light I mean blues in the 400 to 460 nanometer range. When these wavelengths of light hit the colorful algae embedded in the skin of many corals, it causes the fluorescent pigments to release energy in the longer wavelengths 500-700nm, up in the green and red range.
Sure, some of these little tentacled guys contain enough neurotoxin to kill off the population of a medium-sized city, but we love them anyway. If you go by the lethal dose scale LD50, in which the most venomous snake on earth measures up around 25 micrograms--basically it takes 25 micrograms of this snake's venom to kill half of a test population of some kind of animal (Unfortunately, if you're a mouse, this usually means you). So, 25 micrograms for the deadliest snake in the world. For Palytoxin, which many zoanthids and palythoans (these guys in the pics) carry around, the amount is 0.3 micrograms--that's 300 nanograms, or billionths of a gram. And I wouldn't have a reef aquarium without them! I've been keeping and growing zoanthids and palythoans since the late 80's. I'm not about to stop.