I just noticed an explosion of thousands and thousands of these tiny "feather duster" looking animals in the low flow, shaded portions of my tank (BC29). Their total length has got to be less than 2mm, and have a black dot at the center (possibly a primitive oral disk). They grab at the water and wave naturally, collecting food i assume. I just nuked a very small aiptasia (<4mm) out of a zooa frag last Thursday, so I'm terrified hat these are aiptasia larvae. I am not sure at all what hydroids look like, especially when they are this small. Literally thousands of them.