Will my fish or cleanup crew eat my berghia?
In a lot of reef tanks, they'll be fine. Our berghia cleared the aiptasia in a 16 gallon with two clownfish, a firefish, a goby, pistol shrimp, and lots of hermit crabs and snails. Reefers do warn about some tankmates, especially certain wrasses, peppermint shrimp and filefish, and pumps can pull berghia in.
Who lived with our berghia
When we put four berghia in our 16 gallon, it already had two clownfish, a firefish, a goby, pistol shrimp, and a whole crew of hermit crabs and snails. We never saw the berghia again after the first night (that's normal, they hide), so I can't tell you exactly what happened to each one. What I can tell you is that the aiptasia were gone in about a week with all of those animals in the tank.
The egg spiral we lost
At one point I spotted a berghia egg spiral in that tank, which meant at least one of them was healthy enough to breed. I don't think it ever hatched. With that many hermit crabs, I'm pretty sure they ate it. The berghia themselves still got the job done, but if you're hoping they'll breed in your tank, hermits might get in the way.
Tankmates reefers warn about
We've seen the same stories over and over on Reddit and reef forums. The animals that come up most are certain wrasses, peppermint shrimp, filefish and puffers, plus some crabs. Not every one of them will go after berghia, but if you keep them, it's worth knowing.
Watch your pumps
Berghia are tiny, and a lot of reefers say pumps and overflows can pull them in. Covering intakes with a sponge or mesh for a while after adding berghia is a common way to protect them.
If you're unsure about your tankmates, a couple of extra berghia is cheap insurance. The calculator below gives you a starting number.
Still deciding? Read how to get rid of aiptasia (what we tried, what we skipped, and what worked).