I keep OO as a pet in my veranda biotope, which is close to their native environment with stones and water plants.
亀などでしょうか?
例えば「私は亀をベランダビオトープで砂や水草を入れて自然に近い状態にして飼っています」と言いたいのであれば、
I keep a turtle as a pet in my veranda biotope, which is close to their native environment with stones and water plants.
ちなみにベランダビオトープは「A veranda biotope」です。