i have been keeping them since i was 12 and i have kept pairs in 60ltrs it really depends on its size but i would say keep an adult on its own in a 60 as a minimum
and as for ur parents letting u keep one they are very very interesting creatures and can be very educational
i mean they can re grow limbs,reproduce in larva form and never change from there lava form
can ya get any kooler than that?