I would also go with a male threaded to barb fitting, drill a hole in the plastic just slightly larger than the threads, place a washer on the outside, push fitting through from the outside, add a nylon washer, then a rubber washer, then a nut (preferably nylon). Connect a hose to the barb end and place that in a larger container. This is how I made a drain line for my skimmer on my old reef tank. Here is a example of a plastic barb adapter, you can also get them with a built in elbow on the barb end to angle it down if that is a better configuration for you.
