Growing up we had enough space and people to look after a whole lot of pets from dogs, cats, turtles, fish, rabbits and a mongoose. But that was then, now most of us have restrictions that we have to take into account before deciding on a pet.
What kind of pet would you have if you are restricted by space to keep them comfortable and if you do not have too much of time in your hands to look after them?
Goldfish are great. They only need a small tank, a pinch of food every couple of days and to have their tank cleaned once a week. They're a great pet for people with young kids to learn the resoonsibility of looking after a pet and you can start up for as little as $10 including bowl, fish and food.
As wonderful as pets are, my problem is not the space of where to fit them, but rather my lifestyle. I like to travel whenever possible and having to find someone to look after it each time we go would be difficult.
Fish! If you think that you won't get attached to them and learn about their each little personalities you are mistaken. I used to live in a unit, and wanted a pet for my little girl, so we bought a couple of goldfish, and I grew to love them very much. If you look after them properly you can have fish for many years.
A budgie or a cockatiel. You can leave a goodly amount of food and water, you can get away with cleaning once a week if your feeders are good quality ones that don't allow a lot of "throw" and they are just THE most wonderful companions - smart, cuddly and loyal. I love a pet you can handle and interact with, so a cuddly birdy gets my vote and he can spend time with you outside his cage. I raised an orphan pigeon and he never had a cage at all - he sat on his basket handle or my head! (No, he did not poo in my hair - all my birds are toilet trained.)