While sewage pumps are convenient they aren't designed for continuos use and sometimes have a lubrication oil that can seep out and kill everything in the pond.
There are absolutely pumps that can handle this but you have departed from the submersible flavor. You'll be wanting an external pump as the submersibles don't have a high enough flow rate for your application. You will run the input into the pond, likely with a pre filter, and the output to your bacteria filters. Think of it like a small pump house for a pool.
The pump can can be picked up locally at a pond store or aquarium store that deals with large koi ponds.
This is the koi pond store I purchase my pond supplies from and all the filters, pumps and plumbing is available so you can get an idea of scope and cost.
http://www.sdpondandgarden.com/Pumps-External-Pond-Pumps-c-550.htmlEdited by revans2003 - 11/7/15 at 7:42am