Filtration and/or pond vacuuming?

I have 5 KC ducks and am going to build them a pond to swim in. I have two 15' x 30' pond liner tarps and am pretty sure this will do for a 12' x 15' pond with three levels (12", 18", & 24"). My question is how to best keep sediment from building up too much? I'll have a three 20 gal. barrel filtration set up and use barley extract to keep algae growth to a minimum, with a few plants here and there to keep the ducks happy.

Would a pond vacuum be best? If so, what is a good one to use? If not, is there an alternative? I expect some sediment to build up regardless of the filtration, but I am not  sure what is  the best way to tackle it.

Hi Ben,
I'm not an expert, but at that depth, could you just scoop it out with a shovel once in a while? I don't think its possible to keep a duck pond totally clean. Natural ponds will get a bit of a coating on the bottom. Yours could too.