I would not use berghias in your case because the tank is too large and you have too few aiptasia to support a population of berghias, so they would not thrive.

I would use a product and nuke them right away before they spread.

I think peppermint shrimp would be a better choice than bergia since they will starve once you have no more aptasia. Be aware, the non-reef safe camel shrimp looks almost identical to p. shrimp!

I have inject each one with 1ml of vinegar straight from the jug. As long as you get the body it never returns. In my uneducated beginnings I was told by my LFS that they were harmless and even a good thing. So...one of my rocks had a few on it. Killed them all during tank cycling and have only seen a couple since then. As soon as I see one it meets the syringe with vinegar. :) It can be a slow process if you have lots, but very effective in my experience. I've also heard boiling water will do the same thing.

Kevin

I've had success injecting Aiptasia and Mojanos with lemon juice straight out of the fridge
The trick is to blast them dead center before they start to close up
Do it in the middle of your 'lights on' period when they are fully open for ease of injection and less risk of cell release
A steady hand and an insulin syringe are best
Get as close as you can without touching it, or creating water movement, or they will start to close. If so, wait 'till they open
Then, get close and WHAM
It'll shrivel up taking the juice in with it and 'buh bye' pest

I use piclkling lime,suck it up with a syringe and slowly let it go over the aptasia,they take it in as food and it kills them,works not to bad for me.

How much lemon juice?

And how much is pickling lime?

Peppermint shrimp can be hit and miss too I have 2 in my tank one will ignore aiptasia the other will devour any as soon as it feels it.

Maybe 4 or 5 ml
I used an Elos syringe, but it was akward as the tip is pretty large
If I ever have to do it again, I will get a proper syringe from the pharmacy

after reading this thread i just injected some lemon juice into the 3 that are visible in my tank and they certainly didn't like it. I used a pipette and got it directly down their throat before they could close up.

We'll see if its a permanent fix but for now it's clear that they really disliked that lemon juice.