This is what the TBS website says, if anyone is interested:
https://tbsaltwater.com/pages/faq
"Does the TBS farm have Aiptasia?
There are over 13 different species of Aiptasia anemones, from various locations with varying characteristics.
The TBS farm has 4 different anemones. Only one of them has been officially identified.
- The Lightbulb Anemone, Bellactis Lux, comes from the aiptasia family. Its tentacles inflate similar to a bubble tip. LIGHTBULB ANEMONE
- The Sponge anemone, unidentified, is very similar to Bellactis Lux. However, it's tentacles do not inflate, and it is always a dark brown. SPONGE ANEMONE
- A rare black anemone, unidentified, and unlike all others. We do not harvest rock with these creatures, as it is not reef safe. PREDATORY ANENOME
- Unseen during harvests and unseen in the TBS holding system. Occasionally, a customer will report seeing nocturnal small, clear anemones similar shape as an aiptasia. Reports claim they do not reproduce in vast numbers and seem to be reef safe.
Anemones of any kind are not common on TBS Live Rock or Sand."
All that said, that's an Aiptasia 'nem for sure
It's possible it snuck in on something else besides the TBS rock, if you added any other livestock.
I had TBS rock and sand, and I had some of these 'nems pop up, and indeed they did not explode all over the tank like some Aiptasia has for me in the past (and currently lol!). However, when I saw them, I did stab them and inject them with lemon juice, which took them right out.
I wouldn't risk these in my tank, I would take action to remove them. If there's just a few, a needle and syringe loaded with lemon juice or vinegar works well. True Peppermint shrimp (
Lysmata wurdemanni) are natural predators of Aiptasia, but they can also ignore Aiptasia (especially if they are not true Peppermints) and nibble LPS corals and others. Aiptasia eating nudibranchs are a good choice since they only eat Aiptasia, but they are expensive and can become snacks for other livestock in the tank before they take out the Aiptasia. The Nudibranchs are what I'm going to try in my current tank that has some Aiptasia popping up since I have some LPS corals, and the Aiptasia are growing in places I can't get to with a needle and syringe.
Good luck!