Mystery Critter In Tank Can You Identify?

Hi im rasing some killifish fry and recently brought some daphnia to start a culture  3 days into it  i got a shock when i noticed a strange critter in with the daphnia ,hes completley see through apart from his eyes and a brown dot on its head and base so not going to show up in a photo approx just over 1cm in length with 2 visable black eyes and 2 dark dots along his body ,it swims very fast like a fish and the nearest thing i could compare it to is a pipe fish or pencil fish in shape with a type of snout long and tubular ,i thought maybe a type of shrimp but cant see any legs , i would like to put it in the tank with the fry but im afraid it might be preadatory so until identify it its staying in with the brine shrimp,someone sent me a image of some rofiters under the microscope and it does look a bit like the long tubular ones but surely at over 1cm hes to big to be a rofiter ,my other thought is hes a fish fry thats slipped out of the daphnia breeders tank some how
,its a extremly fast critter i think soon it will be jumping its almost jumping at the moment and there are no visable legs or side fins but it is completley see through apart from the eyes and 2 brown dots,can anyone offer any ideas what it may be and if its safe to move iinto my  main tank or should i keep it seperate and see what happens.
 ,it moves regularly and doesnt stop for long and is extremley skittish when scared ive tried taking pics but the camera just cant distinguish it

My guess would be a planaria. look at pictures online and see if that it. If it is then they are a protist that is harmless. 

from what you described are probably glass worms  a good food and safe for your fish.  may prey on very tiny fry.
 

I'm with star. You often get them in batches of daphnia, they're a form of mosquito larvae, and are slightly predatory to very small things, but won't reproduce if you're planning on keeping the daphnia culture going. Only the smallest things like small fry would be at risk.