might be a rock
i have been housing together for 4 years instde enclusure are 1.8metre long
outside is 6m x 2m
room to get away from each other
only problem is with 2 blue tongues fighting
only my experience though
looks like the house gecko methinks, Lepidodactylus lugubris
or mourning gecko
could be wrong though as they may just have changed colour to match the wall
it used to when i lived in chch
i know nothing of the quality of the water though we used to catch trout in there
this is one of the inverts whose presence is used to determine water quality by councils etc around nz