Subject: Questions on testing green tea and beta-blockers in daphnia

I am doing a science fair project testing the effects of green tea and beta-
blockers on the heart rate of daphnia magna... but i have some procedural 
questions that i haven't been able to find answers to.  If anyone could help 
that would be great! Some specific questions are:
1. should i keep the daphnia in one large tank and then put them in separate 
containers before testing or just always keep them in separate containers?
2. how often do i need to test the dapnia in order for it to be considered 
significant? i was thinking everday for 2 weeks and then looking under the 
microscope 2 times
3. Oh and do i need to change the water? some websites say yes and others no 
so i'm really confused on that one

If anyone has any tips or anything i would greatly appreciate it... i have 
looked through so many articles for information and asked my science teachers 
but still can't get any answers!
Thanks again
Elizabeth

Re: Questions on testing green tea and beta-blockers in daphnia