Filling reservoir

I have an 18Gal. reservoir and several 5Gal. buckets...

Is it better to mix nutes with all 15Gal. at once? or can I mix my nutes 5Gal. at a time and fill the reservoir in 3 seperate fills???

Seems silly, but easier to move 5Gal at a time, versus hauling 15-20Gal. around....

What tricks or advice do people have about filling their resevoirs?

why not just mix in the res?????? This Im guessing is not possible.
as long as you mix the buckets the same it should be fine to mix them together... keep in mind each drop of solution wont always have the exact same levels also.. the ratings on the nutes are an average npk reading give or take.....

The reservoir is keep in the grow room and the water and nutes are keep in the other room. It would be more convenient to fill and mix the nutes in the other room.

Do people use small pumps and long hoses to fill or drain their reservoir from the other room?

definatly . I do not personally but Big Ops have timers and pumps for watering soil plants automatically so you could def use a pump to transfer nutes.. My only suggestion is once you get a small sewage pump(NEW) let it pump fresh water for awhile to wash out any manufaturing toxins. GET R DONE!!!!!!!!!