Brandon gives the full details with the photo
here , 1/3 from the bottom of the page. Basically, super glue.
Bigger tank: it's not zoantids, but the hammers and frogspawn are taking too much of space - I placed them in 6g tank, and later has to move somewhere else.
Solutions for zoantid collection placement: Ignasi Torralba
16g tank and same zoantids in
another his tank . Trying to something like that in my tank
Here is how flow influences hammer's and frogspawn's tentacles:
6g cube, flow right to the left, now they have nobody to hurt (at the left of them):

Before that, the hammer was at the right, with the best coral in the center - right on the way of tentacles.
Sweeping tentacle (mine are branching - both hammers and frogspawn):

The good thing is, that they can be placed together - good look and no harm to each other:
