Getting in a bit late here, but I'll add the Eheim 1250 universal pump. I have one in my Brute mixing barrel, the Eheim pump is about 15 years old.
The pump sits in the mixing barrel with RO/DI water, then switched on by a light switch wired to a dedicated outlet.
The pump simply has never failed me, it has never not turned on after sitting a week or two between water changes. When I'm ready to pump to the tank, simply flip the light switch off, attach a length of tubing to the tank. Then flip the light switch on, the switch controls both the Eheim pump and a heater.
I do clean the Eheim pump, but not as frequently as I probably should.
If your using 5 gallon buckets why not just dump it in rather than the hassle of a pump and hose? That's what I do in my reefer 170. Gravity out and dump bucket in . If I'm not feeling strong I dump 1/2 a bucket at a time. Just dump slowly and nothing gets stirred up.