Ethics of using Daphnia (for C/W)

I doubt this will get any respones but here goes anyway:

I'm doing my bio c/w on the effect of caffeine on the heart rate of Daphnia. I was wondering if anyone knew the ethical implications for using Dapnia/treating dapnia with drugs, they are invertebrates btw.

I've googled but found nothing decent. Thanks in advance to all who reply

There are no laws at all that protect water fleas!

I remember doing this experiment for my A-Levels, waaaay back when! We used caffine and alcohol though

lol...yer but there's a little section where I have to write about the 'ethical implications of the choice and treatment of living organisms and the enviroment'
what the heck am i supposed to write!

Just say that you keep them in a natural environment as much as possible, don't expose them to the drugs for too long, put them back into the wild once you're done, keep them damp and cool (this is especially relevant when you're putting them under a microscope because of the heat from the light), don't expose them to unnecessary stress e.g. poke them... (sorry, I'm too tired to be really serious about water fleas!)
Maybe a mention of some people considering them God's creatures and so should be respected?