I keep a female Gonyosoma boulengeri since 2013, I got her as a youngster and she has grown to about 120 cm (ca 4 ft) now. I keep her pretty much as Zincubus describes it. Currently she is still in a smallish exoterra enclosure (90 x 45 x 90 cm / 36 x 18 x 36 in), ReptiBark as substrate, some branches, some real plants, a water bowl. As Zincubus already said, she spends a lot of time in the water.

I use a T5 florescent for basic light and a 75 W Metal Halide Light to provide a hot spot and UVB. I don’t use any other heating. Under the MHL the temperature might get as high as 32° C (90° F) while the opposite side of the enclosure is room temperature (usually around 23° C / 73,5° F), providing a horizontal and vertical temperature gradient for the snake. I found that my snake will bask directly under the MHL for some time and then move to cooler places. On general terms, they don’t need high temperatures, but will use a local hot spot. You should bromate the snake for some weeks, not a really cold brumation, but with reduced light, reduced temperatures (especially during the night) and no food.

Tubs is in my opinion a bad idea, especially for an arboreal snake. Everything coming from above is usually a bad thing (like bird of prey), so opening the lid to do your maintenance might stress an already nervous snake and provoke defensive actions like fleeing or even biting. A front opening enclosure allows you to work from below the snake, so it will usually stay more calm and relaxed.

I feed my female with medium or large mice and sometimes with day-old chicken.