you provided pics of 2 different types of garter snakes.

looks like the top pic is a red sided garter and the bottom pic is a san francisco garter (very very rare and endangered).

garters really arent aggressive but can be a little nippy and can be more high strung (wiggly) than things like kings and corns.

I wouldn't put one in a fish tank though. the garter would eat all of your fish and they need dry land and place to bask like most other snakes.

now if you had a huge cage with maybe 75% of it dry and a small pool on one side for the garter to swim, that would be nice.