I have allways been intrested in balls, i think there great but in the past a few things have put me off,i wondered if you could take some time to answer a few of these

1.how big do they grow on average
2.i have a dog and my mum and dad are saying if it escapes it could attack or strangle the dog :S i would never forgive myself if something happend.
3.how much for absoplutly everything would they cost on average?
4.what size tank do they need for a full adult?
5.is there any other balls that are cheap enough that have nicer colours lol not that they dont but any other colours?

thanks