If you really can't blow it away with some good blasts, I don't think it's dino's then. Doesn't totally look like it, the photos are a bit rough TBH.
Do they also disappear at night or no?
Try to make your lights WHITE and take off all blue, and take the photo completely level so you are parallel with the tank glass.
Might be GHA or some similar type of Algae.
Alright.... I haven't stuck my hand in this tank since September this year..... This is in no way an ode to my horrible husbandry, I'm only mentioning it because there's a lot to be said for KISS in Saltwater and just letting a tank do it's thing. I've fed it. I don't know every 3 days...
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