No, it does not need to be air tight. You can put more than one set of filters in it, if you wish, but one is what it comes with, originally. Make sure your pump is not doing more than 1000 gph. Also, the outlet is on the bottom, and is 1.25" in ID. The inlet is on top and can be 3/4" to 1". Do not attach anything after it, and run the outlet tubing downhill, at least slightly, to the pond or waterfall.
Date published: 2018-05-10