What kind of alg is this?

[clownfishforever]

Aquarium
- Nano marine tank
- no fish or coral
Size: 40x40x40 cm
Duration: 2 years
Equipment: Fluval C4 power filter

Hi! I'm Emin from Turkey. I have an interesting living being that I've never seen before and I need your opinions about it.

This caribsea rock had been in my another tank for six years, but because a kind of harmful bubble alg appeared on the rock, I put it in this tank without any cleaning two years ago.

Surprisingly, this weird alg, or whatever it is, appeared by taking root inside the bubble alg six months ago and it has grown up since then.

I and my reefer friends have no idea about what it is.

I'll be glad if there is anyone who saw this before to acknowledge me.
Thanks in advance for your help.

 

[sixty_reefer]

It’s caleurpa, popular as a refugium algaw

 

[WheatToast]

Caulerpa brachypus, also known as sea mustard and mini Caulerpa. This is a very uncommon Caulerpa species that I have found to have a very low risk of going sexual. It is slower growing than my Caulerpa prolifera and Caulerpa paspaloides and can form gorgeous carpets on the sandbed and rocks, though still has the potential to become invasive (@dvgyfresh had a Caulerpa brachypus infestation once). It is probably a good refugium algae.

 

[clownfishforever]

Thank you for your help and this information. The alg (caulerpa) grows up very fast. I'd like to share its video. Thanks again.