Im pretty inexperienced with snakes, only 1 diamond but the waterfall is something i can help with. I have kept marine fish tanks all my life and use water falls in my indoor 12ft wide 3 foot deep shark pond. If your going to go a bilge pump or the like, remember they run hot. they are really designed for short quick bursts and i have seen them fail heaps when used in this scenario. I would suggest the canister filter as the first choice for pumping. You set up the reservoir in a bowl shape. i often use a cheap funnel as the base of my mold, cut off the long spout leaving about 2 inches on the end.
Connect the intake hose for the canister filter to that.
then put the output up to the top of the fountain. I pour the output into a shallow bowl and then let it overflow to the fountain as I believe it looks a little more natural.
This is especially good for reptiles because otherwise the water can get real dirty real quick if your snake likes to have a bath J
My personal preference is the aqua one pond filter. It has a large filter medium capacity and they last forever and a day but they are pricey. The cheaper ones like the boyu and ebay models are ok, but be prepared to replace them roughly every year as the magnets that run them eventually overheat, fail and the thing is a throw away. At least with the aqua one there is parts available.
As for molding. I basically go to bunnings for open flow waterfalls and go straight to the plumbing section. Using all the elbows and y pieces I make up channels for the basic shape. Just adjust the size of the pipe to suit the job 35mm for small fountain and 90-110 for large fountain. Be adventurous. Don’t go with one size, use reducers to get high flow areas.
Once you have that done take it home and use plumbers glue to glue them together. Use a jigsaw to cut the tube in half. If your super keen you now have 2 waterfalls.
For the formwork I use concrete and sandstone pieces to make up the outside around the pipe up to where the edges of your cuts are.
Then get hold of some acrylic texture coat or bucket render (I use Wattyl ready render) and rough coat the whole thing.
Final step coat the whole thing with waterproofing membrane. Which you can buy tinted to any colour. I try an mix a few colors around to get multi level effects but I have heaps of it lying around.
As a final note, if the stone/concrete is to heavy. And even a small one can be really heavy. I mold from auto body filler or fiberglass but with the fiberglass you need to be extra careful or the water will leach into it and it will eventually disintegrate.
Hope this helps. Pm me if I can help further.
Cheers
Jamie