Rubber Couplers can be used in your pond plumbing anywhere that you might require a disconnect.
Joined easily with steel clamps, these couplers provide an easy solution to disconnect the piping at a particular juncture in order to perform maintenance, remove a clog, etc.
If you have a heavy fish population or low circulation in your pond, consider supplementing with extra aeration. This can be in the form of a waterfall, fountain, or simply an air pump.