For the last two years my year 9 Science classes have constructed and observed bottle ecosystems. We cut up 2 2 litre bottles and had the top part as a terrestrial system and the bottom half as an aquatic system. We keep some small fish in the aquatic system. Last year they all survived. This year about half died. This happened quickly and also occurs in the big communal tank I had for the fish, so this was probably due to factors beyond my control. It’s a really motivating activity for the students, which is why the loss of fish was disappointing. Students identified ecological factor, made predictions and follows them through.