Yeah, that won't work (BRayPond's diagram). The arrow you have going from the pipe to the pump is the path you wish the water would take. But it takes the easiest path and that would be above the gravel. So the pump wouldn't draw any water out of the pipe and therefore the arrows at the bottom showing the water going into the pipe wouldn't happen. You end up with the same result whether the pipe is there or not.
Like Addy said, 2 pumps can be used. The vertical pipe in your diagram would be replaced with a large enough diameter pipe that you could place a pump inside and let it go to the bottom. The vertical pipe has to be extended above water level or the pump will just pull water from inside the pipe, least resistance, the water would just circulate inside the pipe. You could in theory extend the vertical pipe all the way to the waterfall if the design will allow. You need a basically straight shot to the pump for maintenance. The pump cord is long enough too.
The second pump, at the bottom of the gravel, can also be an air pump. Cheaper to run, very tricky to install.
I call this a down flow filter. Not optimal because it draws your worst water, on top of the gravel bed, down into the gravel.
Up flow, singe pump.
I like simple. This diagram is what I call a catch basin.
It forces the water from the falls down into the bottom of the pond. In your case you would have a gravel level above that bottom arrow and your bottom pipe with holes. No vertical pipe. Basically the catch basin acts as your vertical pipe and the water flows in the opposite direction. Your pump could be placed anywhere you like in the pond. I like it in the skimmer. If on the bottom the pump clogs and could drain the pond if something bad happens.
In this set up water with the most O2 goes to the bottom, into the gravel to help bacteria. It's the cleanest water if any filters are added before the falls so gravel doesn't clog as fast. The up flow pushes, in theory, stuff up off the floor, out of the gravel. Self washing, in theory. In reality it's doesn't help much without a huge pump. But still better than down flow I think.
The other benefit to the catch basin is a very still surface which makes viewing the fish better. I got the idea from high end Koi keepers who floated a rope on the surface around the falls to stop ripples. The catch basin also collects any foam instead of having to see it floating around the surface.
I build the basin with mortared rock. Pretty easy to build, nothing fancy. Here's a picture of one completed.
You can see how still the water is in the pond and how the bubbles aren't floating around.
Like Addy said, 2 pumps can be used. The vertical pipe in your diagram would be replaced with a large enough diameter pipe that you could place a pump inside and let it go to the bottom. The vertical pipe has to be extended above water level or the pump will just pull water from inside the pipe, least resistance, the water would just circulate inside the pipe. You could in theory extend the vertical pipe all the way to the waterfall if the design will allow. You need a basically straight shot to the pump for maintenance. The pump cord is long enough too.
The second pump, at the bottom of the gravel, can also be an air pump. Cheaper to run, very tricky to install.
I call this a down flow filter. Not optimal because it draws your worst water, on top of the gravel bed, down into the gravel.
Up flow, singe pump.
I like simple. This diagram is what I call a catch basin.
It forces the water from the falls down into the bottom of the pond. In your case you would have a gravel level above that bottom arrow and your bottom pipe with holes. No vertical pipe. Basically the catch basin acts as your vertical pipe and the water flows in the opposite direction. Your pump could be placed anywhere you like in the pond. I like it in the skimmer. If on the bottom the pump clogs and could drain the pond if something bad happens.
In this set up water with the most O2 goes to the bottom, into the gravel to help bacteria. It's the cleanest water if any filters are added before the falls so gravel doesn't clog as fast. The up flow pushes, in theory, stuff up off the floor, out of the gravel. Self washing, in theory. In reality it's doesn't help much without a huge pump. But still better than down flow I think.
The other benefit to the catch basin is a very still surface which makes viewing the fish better. I got the idea from high end Koi keepers who floated a rope on the surface around the falls to stop ripples. The catch basin also collects any foam instead of having to see it floating around the surface.
I build the basin with mortared rock. Pretty easy to build, nothing fancy. Here's a picture of one completed.
You can see how still the water is in the pond and how the bubbles aren't floating around.
