Similar to the type base I made with concrete only you do a lot neater work!
link to thread with my concrete diffuser bases The only think I would do differently would be to either make the base thinner and bigger footprint or else combine a plastic disk or something for a bigger footprint.
With yours being extended up above the bottom they will be fine. But such a small heavy base tends to sink down into the much in the bottom of the pond. I have a plastic concrete mixing tub to put under one of mine but I have never installed it. I used to have a little problem with the concrete diffuser base stirring up sediment but I have not noticed that recently. Maybe it has cleared out a big enough area around it so it does not do it any more. But a heavy small footprint base will tend to sink into soft muck or clay.
