Zoanthid palytoxins.

These are extremely dangerous, but on the other hand it’s not common for them to be of any great issue if treated with respect.
If they will stress in your aquarium, then many other aquarium life forms will stress due to the zoas being a very hardy form of reef life, so if the zoas stress, what made them stress will possibly kill other life forms before them.

It’s best to use algae to import/absorb all naturally forming/excreted and inorganic toxins, if you have a little in some in place and maybe a little activated carbon, then you are protecting your reef life, as for people, you usually need cuts for the toxins to enter you or they squirt when out of the water into a cut or an open area of you when fraging or what ever, to let in toxins.
Just always wash your hands when handling any soft corals before scratching your eye or touching any thing else beyond your self as many corals can kill or partially harm us humans.

If you are concerned some one like a child may touch them in the aquarium, make a net cover for my aquarium, or you could get some egg crate to use as lids so air gets to it and nothing else.

Some local zoanthid photos.
https://southeastqueenslandm.aforumfree.com/t2089-zoanthids-common-in-seq