I think I'm pretty much out of berghia. They did do an AMAZING job on my aiptasia forest though.
Here are my recommendations:
Order a LOT. Don't bother getting the more expensive 1/2" ones (breeding/egg laying size) - if you have pods in your tank (who doesn't?), the egg strands will get eaten. Plus, on my second batch (yep, I ordered TWICE - about 5 weeks apart), I only ordered the 1/4" size, and they were all larger than that anyway. Plus they grow SO fast.
If you order through Salty Underground, ask Lisa if you can get a quantity discount and/or a few extra thrown in - that's assuming you order 10+. I ordered 8 originally (half 1/4", half 1/2") - they made a dent, but they dwindled... probably because I wasn't checking my back chambers for wayward travelers. The second batch wiped out the rest (or at least the vast VAST majority), but I was pulling stragglers out of my back chambers every single night.
Do they work? You bet your sweet arse.
Are they pricey? You bet your sweet arse.
I'd recommend a group buy (wish I would have done that - instead I ordered corals to help lessen the shipping pain x2 - for what it's worth, the corals they sent were GREAT)
If anyone has any questions, let me know. I'm not an expert, but I can at least pass along some of my experience. I kinda miss seeing the little critters crawling around, but I DON'T miss seeing those darn aiptasia!