I put mine in 90x45x60 when he was 40cm, just make sure plenty of cover, I've got loads of fake plants, warm and cold hide, and hanging basket fake plant from roof and he climbs around everywhere, as he gets older I'll take some out as the fake vine plants won't hold his weight and he'll need more open space, but yeah so long as you give them heaps of areas to hide should be fine.
Mine has big corner water bowl that he can swim in and will be able to swim in even with an adult, picked corner stone one as takes up least floor space while giving most swimming room.