I did 2 at our place to get the feel of it.
Especially after all the hype about filters.
But I did ours withour filters and found that the water stays crystal clear most of the year once its system gets balanced.
Then in two books by two experts, they indicated that filters are not needed if fish will not be included.
The home pond showed us how fast the pond plants cleared the water after it started to cloud a bit.
Although that was the back pond. The front pond stayed clear continously for 2 years without any plants, and a couple of goldfish.
A good mortar training area too.