I do something kind of similar, a little more ghetto. I have a 2 liter and 3 liter soda bottle that I rinsed out, and peeled the labels off. I threw away the caps, cut off the bottoms, and poked a hole on opposite sides of the bottom of the bottle and fed a piece of stiff wire through each hole . I float the bag for a half hour, then grab whichever soda bottle better fits the bag. I attach the bottle to the side by bending the wires over the edge of the sump. . I make sure the wire holes are above the water line, but the majority of the bottle is submerged. Open the bag, dump out some of the transport water, roll down the top a couple of times. Place the bag in the bottle. Drip from the tank into the bag. Use a turkey baster to remove water as the bag fills. Usually drip for about a half hour or so. Negates any possible temperature issues, since the bag is suspended in the tank water in the sump the entire time.