Re: What dose of steroids do I use on Daphnia?

Do you want to improve their ability to lift weights?  What endpoints are
you looking for? That is, what effects are you looking for? If I were you,
I'd look at dose rates for the steroid of interest- in mg per Kg which
should be in the physicians desk reference or somewhere similar and I'd
consider the water they are in to be the thing you are dosing. For example,
let's say the steroid you want to dose the water fleas with has a suggested
dosage of 1mg/kg. If your Daphnia are living in 1 Liter of water, I'd add
one mg of the steroid in one treatment. I'd also try a liter of water with
Daphnia with 0.1 mg and one liter with Daphnia at 10 mg of the steroid. Of
course the suggested dose per Kg is likely to be different with whatever
steroid you are looking at. 

The next issue is what are the endpoints you want to measure- reproduction
(how many babies), survival- how long the critters live, resistance to a
bacterial challenge- how many survive a dose of bacteria that would
normally kill half of the Daphnia that get them etc. So you've got a lot of
thinking to do.