making a pond cleaning pump

I'm thinking to build a small centrifugal pump to suck in dirts and algae accumulating at the bottom (concrete) of my pond. Commercially
available centrifugal pumps are too heavy and too expensive. I plan to use an old but working 1/2 HP induction motor directly connecting the pump. Please help me designing the shape of an impeller (about 4" diameter) and where I can get a sealer and suitable bearing.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.