Are there saltwater fish/freshwater fish comparison experiments
 

I can do at home?

If Tex thinks I am strange, I wonder what he thinks about you!!

I have no idea what you are talking about. You will need to explain further.

I need to pick an experiment for a biology class.

I'm interested in fish, and I know that saltwater fish and freshwater fish function differently. I can buy both of them at a pet shop. Is there an experiment I can do at home to test differences between the two types of fish?

it doesn't sound terribly ethical if it will involve killing fish and not add to humanity's body of knowledge. I would move on to a different idea. Not to mention it doesn't sound like you have aquarium setups.

I just bought an aquarium setup and 10 gallons of saltwater. It'll take at least a week, I'm told. The whole thing cost me $150. I might as well keep fish for a while after the experiment.