what is this thing??????

Sounds like a pod explosion to me... Especilally if the fish and star are eating them, good food!

 

They could very well be copepods. Take a look at this picture. The smaller "bugs" are copepods but you won't be able to see them this up close and personal without a magnifying glass:

 

Great pic, amcarrig! You can even see the smaller copepods among the larger isopods.

 

I only wish I had taken the picture buuuuut...I didn't.

My picture still doesn't beat the one that you posted of a gravid copepod

 

Yup. I had to take him out to dinner to get him to hold that sign!