Why slow as opposed to fast? How critical is my fuse choice? I've been told at least a dozen different things as far as amperage, slow vs fast, casing size, etc. I hate to just resort to the 'any fuse is better than no fuse' mentality.
Within the first second or so of the pump starting up, there will be inrush current perhaps 3 to 4 times rated current. That's why its good to have a slower acting fuse ... it'll still protect the circuit against overload but won't blow during startup.
After 10 sec or so, they're all the same, but check the difference here at 1 second:
