absolutely, just throw in some plecos, flagtails and high powered lighting to enjoy viewing, and you'er all set.
is what i really wished i could say...
unfortunately, i have to say this instead..:
in short no. 90gals is going to be too small for a shortnose gar. and those are pretty poor tankmates. if you had bothered to use the search tool, you'd have found many threads that would have told you exactly that. but i digress..if you want to try keeping gar, then i'd highly suggest starting with a florida gar. but definately get a bigger tank first and do not mix it with those fishes.