Excellent video demonstrating density and heat transfer of liquid!

Can view the video here if the embedded one has problem: http://www.youtube.com/watch?v=ZH96MhITOlk

Pointers:

• Oil is less dense than water, hence it floats as a separate layer on top.
• Heat transfer in liquid is mainly via convection currents.
• As the oil is heated on top of the water, very minimal heat is transferred to the water as there is no convection current generated in the water.
• The goldfish tends to stay at the bottom of the tank. Guess why?
• Question: Where does the goldfish obtain the oxygen?