well chameleons dont really care about any other animals in their cage, especially a little jacksons with a peacock. and the day gecko wont really care about any other animal unless its a male of its own species. i kept two adult standings(10 in long) with an adult ambanja blue panther who was big enough to eat fuzzies in a 30g x high. they were always happy and minded their own business. they d be perfectly fine as far as aggression, but they come from different environments. your jacksons needs it cool and the day gecko needs it hot. the day geckos a lot hardier and can tolerate a wider range though. a 10g is more than enough space for a par of peacocks. but the best way to learn is to try it out if you are confident that he wont eat the gecko.