fuse on battery

I recently got my vehicle back from my mechanic and realized he took the fuse that is connected close to the battery out and forgot to give it back. I have no idea what size it was or what size I'm supposed to use to replace it. I am running just a small 200 watt Memphis SRX1.250 system. I know...

I hope crossfire amp is good.. he added 2nd battery and bigger wire from alt to bat WITHOUT A FUSE!! I told him last nite had to have fuse on all pos + wires coming from alt and on 2nd bat coming from 1st batt and he needed another ground on 1st batt (he did 1 ground from 2nd bat to motor) no...