[Monica]

The largest cage that you can afford that still has the required bar spacing for tiels. A cage that is longer than it is tall (rectangular in shape, if not square) is best as well. Now saying that, a tiel should never be put in a cage smaller than 2' square (i.e. 2' x 2' x 2' approximately).

So with that in mind, try for the largest cage that you can afford (may want to check out ebay, or local adds for birdcages as well).