Since then, we (4) have been working/ worked on making a robot that will be able to kill lionfish with electricity.

We already (5) tested/ have been testing the first model but it didn't work very well.

There are no animals that naturally eat the lionfish here, so we (2) have been trying/ tried to train sharks to eat them, but it didn't work.

The sharks only (3) wanted/ have been wanting to eat the lionfish if one of our divers fed it to them.