HI guys. Thought I would answer a couple of the questions you are asking.
Copperbanded butterflys and aiptasia... If you get one to live more than a few weeks you are doing well. Only about half of them that live will touch the aiptasia. Half may also go for some of your corals, etc. All will clean your tank out of the small feather dusters and worms growing on your rocks.
There is a general rule that says if the creature might eat aiptasia it might also eat berghia. This includes butterflyfish and peppermint shrimp. It is not recommended to have both berghia and one of these together in a tank, especially a smaller tank.
Some wrasses, and really any nocturnal aggreessive carnivore, might also eat berghia. This includes some larger coris wrasses, arrow crabs, sally lightfoot crabs, etc. Berghia do not taste good to fish since they taste like aiptasia. But just the act of placing them in their mouth and spitting them out can injure the berghia.
Not all wrasses will bother with berghia. I have successfully had berghia in my own display tank with a Christmas wrasse, mystery wrasse and possum wrasses. The coris wrasses and some of the lined wrasses seem to be the most aggressive rock pickers.
Berghia life span in a display tank is about 6-8 months. They are typically about 2 months old when we ship them.
If you want to set up a tank just for the berghia and your aiptasia rock, you should keep the temp around 78 degrees, with just a little water movement. An airline hose with no stone is perfect. Mind the water quality just like you would your display tank. Keep the tank clean. The better the tank maintenance the more likely your berghia are to thrive.
We have plenty of customers who are successful with berghia. They are not the perfect solution for all tanks. But they are a great solution in the right tanks. I hope this info helps you identify if you need to make any changes before you buy berghia.
Please feel free to post more questions, PM or call us to talk more.