Hi,
What size enclosure would be recommended for a hatchling?
How long are they to be in said size enclosure?
What would the next size enclosure be?
How long in that enclosure?
Adult size enclosure?
What age are GTP’s sexed?
Is there any way to tell the sex just by looking at the animal?
Sorry to bother people with all these questions.
Thanks in advance
Happy New Year and welcome to the forum! So glad you found us! Don’t ever apologize for asking questions! That’s what this forum is all about! Asking for advice and sharing knowledge!
Unfortunately I have no experience with GTP’s but I’m sure there others here who can help you! I just wanted to welcome you! 
Hi! Welcome to the forum! I honestly know nothing about these beautiful creatures but I went poking around in some older posts and did notice a mention from one of our knowledgeable and respected members here who is or was a GTP breeder, who I mention below.
I am tagging @osbornereptiles in case they are available to help.
I’m sure there are others here that are familiar with these snakes who may be able to help with your question.
Happy New Year!
Me again. I don’t know what keeps drawing me to this post but here I am lol. I’m not sure if anyone else will end up chiming in. So I did some more searching and while it does not answer some of your questions, it seems to at least give a rough idea of what others use for enclosures.
I can’t help much with the other enclosure sizes but the bare minimum for an average sized adult is a 2 foot cube. however, I think that if you can get a 3x2x2 or 3x2x3 that it will be an overall more ideal enclosure as the can get relatively large.
I believe that they can be sexed at any age but as green trees have very fragile tails, you have to be very, very careful especially with hatchlings. I do not believe that you can sex them visually.
I don’t know if it’s the same for GTPs but I’ve been advised by ATB breeders that they do best in a good sized tub for the first year, then move onto their adult enclosure. Add as much cover and foliage as you can to help them feel secure. I know they’re different species but very similar in terms of care and size. I agree with logar’s adult enclosure sizes, if you can then a 3’ high vivarium is great, they do take advantage of the height.
No breeders over here even attempt to sex their hatchlings, and I often see even yearlings for sale unsexed, so you might have to wait a while and get someone with experience to probe yours.
Set it up in something like this. It doesn’t need natural branches this one was for an ATB, you can use closet poles or pipe for a GTP.
Species makes a difference in maximum size. Aru animals are pretty small, Biak animals are bigger. Designer (mixed) animals can be anywhere in the spectrum.
GTPs are not big snakes in the wild. People get them way too big in captivity. A 2x2 cube or a 2x3x2 is all you need for an adult.
Thank to everyone that has commented on this post. I really appreciate your responses. You guys have helped a lot.
Thank you 
I’ve been keeping GTP since 1996. I’ve personally bred captive animals and wc imports with equal success. This is only my personal experience, and I’ll say some of it goes against the “standard” for the species.
Hatchlings through yearlings should be raised in plastic tubs on paper towel, with a simple grid perch and water dish. This is all fluid because of individual growth rate and you may have animals large enough to move at 10 months and some that may take an extra few months.
Adult size enclosures can range from 16 x 24 x 16 and up. Again, my experience is large cages aren’t utilized much by this species. Some animals would literally sit on the same perch location for months at a time, eat and drink from the same location, and only move during a shed. I tried a variety of adult cages and the animals preferred 20" to 24" cubes over all other sizes I tried. For really large females a 30 x 24 could be optional but not necessary. In my years of breeding GTP I was successful in arboreal 16 x 24 tubs, 20/24" cubes, 30x20x20, 40x20x20, and 36x48x16.
Animals can be safely sexed at around 100g. This can be anywhere from 8-16 months. It seems like people are too afraid to try these days but it’s relatively easy to do.
Good luck should you choose this endeavor. It can be extremely rewarding and heartbreaking at times.
I have been keeping &breeding gtp since the late 90’s as well &i learned to start keeping my hatchlings in shoebox sized tubs with bare bones environment like mentioned above… paper towel, water dish &plastic perch for easy cleaning &monitoring. They are very finicky at this age &will need to be watched over as far as eating, pooping, possible regurging, ect. They are much like a pet goldfish in the fact that it will feel much less secure in a big open area. I know that obviously in the wild it is born into a large open area but you also have to understand that very few out of a clutch will actually survive in the wild, only two snakes out of a clutch of ~15 will need to survive to repopulate in order to replace their parents. In captivity we strive to have far less of a mortality rate so making each snake feel comfortable &secure is a must otherwise you will have all sorts of problems. &in each wild area there are multiple microclimates or biomes which would interpret to a much smaller enclosure in captivity. I then move up to a medium sized rubbermaid or sterilite tub after a year to 1.5 years of growth, then a larger one after about 3 3.5 years before finally placing them into their final adult cage at about 4.5 to 5 years. This gradual increase is very important &will help your gtp feel safe &secure in its own little area &will greatly decrease the amount of problems you will run into woth raising these little guys. &they do stay very small. Even some of the biggest gtp i have seen do not look much larger than a normal 4-4.5 foot boa or python when they are curled up on their perches, where they will generally stay for most of the time.
Another big factor is perch size… you do not want to start out with a big branch or perch circumference. For a hatchling i would recommend a perch size of no bigger thickness than a pencil, thinner than a pencil is best. What you are really going for here is for both sides of the snake that are perched over the branch to be able to come in contact with eachother for at least a half of an inch… inch is better. Not only does this make the snake feel more secure but thicker branches or perches can actually cause a seperation of the vertebrae of the tail, resulting in either a kink or possible necrosis of the tail tip which is something you definitely do not want with an arboreal snake who uses all of its tail for locomotion. Is it completely going to ruin its chances of climbing or living a complete life, no; but it will definitely inhibit it &there will be lost time in the case of it needing to heal or come up with a new plan for locomotion through the treetops.
Also it looks goofy as hell, lol.
Anyways, I hope that this gives you a little bit more of an insight into the keeping of these wonderful animals &helps you lots along the way. As said by the previous poster these are both an extremely rewarding yet supremely heartbreaking species to work with at times &any extra bit of knowledge helps.
Skòl,
MP3
Holy cow those guys are stellar! I am totally in love with the yellow guy! Love the finger wrap! 
