Apparently, the lid of the tank to the filter is quite easy to lift up. Lizard could have wanted to have a dash of water or a swim (that would have been silly). So it lifted up the lid and 'goldilocks! there's a big hole and i can't reverse gear!' End up dropping into the anti-chlorined and medicated green water. Poor thing as the 2 stunned parrot fish watch it sink to the depths of the tank without being able to help. The fish have never seen a land creature swim in their midst before. And so, the lizard drowns and dies. Traumatised me had to lift it up with the fish net. Sad story.
