When I change their bedding, which is when I think the general look ain't fresh anymore, not sure how long that takes, depends on the size of the viv and the snake(s) in it, but maybe every 2-3 months. I used bleach in hot water in the past but recently switched to cleaning vinegar since I think it is better for the snake than bleach. I have Herpteks so squeezing a few sponges of water with vinegar into it, than rubbing the viv with a rough sponge for a few minutes is enough. Then I leave it for about 10 mins to 'kill the bugs' and absorb the water with an old towel followed by 10 mins of drying et voila, viv cleaned.