What would be the best way to set up filtration for my pond?

[Carefree_Dude]

I recently moved into a place that has an old pond with a stream. The pond is roughly 400 gallons. There is PVC that connects to a sump pump that pumps water roughly 20 feet away, and then the water goes down a little stream and back into the pond.

The only thing in the pond is a few frogs. I just drained it, shoveled out so much sludge, and have it partially filled now and the stream feature working again.

What would be my best option for proper filtration for this thing? I was thinking maybe putting a few goldfish in it, and letting the frogs stay. There is also a pine tree above it that drops a ton of pine needles.

 

[AaronKWolfe]

I'm afraid the pine needles might make the water acidic, so you may need to watch out for that. Just check your water parameters, make sure the water isn't too acidic. As far as your filtration goes, I think a mix of plants (duckweed would be fantastic, goldfish love duckweed) and a sump and/or canister filter would be good. It is a bit difficult to say without seeing your setup or a better description.

 

[Carefree_Dude]

Here it is

 

[Fishman Dave]

Easiest would be a box filter covered in stones at the head of the stream. Would just need to amend the pipe work there to pass the water through the box filter. To be honest, lilies and marginal plants may do a better natural filtration job and use the running water as airation for the fish since you may find with natural ponds that you are always cleaning out the box filter.