Many people like the idea of building their own pond filter, just make sure you avoid these things in your pond filter construction.
Many people will make a filter much to small, or too large, for their area. Take accurate measurements before you start on the pond filter construction. A filter too small will not be able to handle the filtration of a large pond, and a large filter will not be cost-effective for a small pond.
The flow rate is one of the most important aspects for a filter to work properly. A flow rate that is too high can damage the ecosystem by killing needed bacteria. If the flow rate is too low then it doesn’t serve the purpose it was designed for.
Where you place your filter will determine the flow. You want it to be circulating as efficiently as possible. The best way to do this is to ensure that the filter is placed above the maximum water level. Consider utilizing waterfalls or other natural flow devices to assist with the flow.