Sadly, I believe those are large cell amphidinium. But hopefully I am wrong. @taricha can confirm.
Tough, ugly buggers. UV won't help. You can read through this thread to choose your favorite approach, but expect them to persist for quite some time. On the bright side, they are not toxic so nobody is going to get hurt by them
Amphidinium Dinoflagellate Treatment Methods
This thread is a spin-off from the @mcarroll very successful Dino thread The purpose is to discuss methods for removal and fighting against a particular strain of dinoflagellate - Large Cell Amphidinium. It seems to make up about a third of the cases of dinos. The reason this strain gets its...www.reef2reef.com
Dang, alright.... Looks like going to be a fun ride.