Just thought I'd chime in to say that it is recommended to keep at least 4 as one, they are colonial animals and eat by ganging up on one aiptasia and secondly, for them to easily find each other and breed. Berghia does not feed continuously once fed. The aiptasia will split faster than the berghia can consume them.
That is why it is important to keep in mind that it is not the berghia that you purchase that will take care of the aiptasia problem, rather the offspring of the parents you first get that will ultimately decimate the aiptasia population.
Guys thanks for the advice I appreciate it.
Just want to have little bit fun seeing that nudis eating aiptasias
I can drain that frag tank in 5 minutes and scrape aiptasias from the glass but this will be too easy