Not sure about the gar, the length of time the silver can spend in the 120g will depend on the tanks dimensions and how big the aro is now.
Minumum the tank should be about 3x as long as the aro and have a width/depth that is equal to the length of the aro. Silver aros grow an average of 1 to 1.5 inches per month.
silvers with gars are very common. make sure they are either both small, or both medium, or medium silver with not too small gar. basically make good judgement on who can eat who, and don't put a baby with a giant. they live nicely together. i have 3 silvers with 2 spotted gars and 1 shortnose gar. they all get along great.
I have a 6" red aro with 2 5" florida gars in a 50g grow out tank and the aro sometimes takes a bite at a gars tail (especially during water changes and has never actually struck the gars) but overall he leaves them alone. In a bigger tank (270g when they are bigger) I don't think I'll have a problem. A silver would probably act the same way with gars.
To all who seem to be building their post count by stating the obvious. He already know that a bigger tank will be needed Comprehension of the OPs question is definitely lacking.
ArowBichir;2856127; said:
Hey everyone,
I was wondering if if i could keep a sliver arowana with a spotted/florida gar together and how long can i keep them in a 120g