I hate to say this but i have this problem as well.

Not even 2 days after putting new organic soil into my tanks i have about 20 of those things in there... as soon as i open the screen top they swarm in my face. So if you find a solution to this problem ID LOVE TO KNOW. If only I could put darts in my tree frog tank. They would gobble those things right up! (NOTE: I DO NOT HAVE KNATS IN MY DART FROG TANKS! NONE OF THEM!

I think thats the only solution without chemicals..... haha sigh... wouldn't it be nice to have an all natural eco system and mixing species of frogs >.<.

AS FAR AS THEM BITING: NO id think not... They breed and eat stuff in the soil. (as far as I know)
AS FAR AS THEM ANNOYING /PESTERING THE FROGS: Yes. My dumpy's HATE THEM!!! Dumpys always try to kick them off with their legs. I see it every now and then. No bite marks or reactions so I think they are just landing on them.

As far as my red eyes...they make no notice of them. For my rubys...they make no notice of them....for my green tree frogs and baja california tree frogs... no bother. Darts of various species: DINNER BELLS START RINGING!