I'm not sure if it's truly a "bog garden", but the top of my waterfall is a barrel liner filled with pea gravel. The water is pumped to the bottom of the barrel and flows up thru the pea gravel. This is my filter. The store that I get my supplies from recommended this and it has been working fine. Take a look at the pics.

Deb in PA

Here is a link that might be useful: my pond

Bog is seperate to pond,its a whole different wetland. You might be thinking marsh? Marsh plants make great buffers.

I have a 100 gallon skippy type filter that flows into a 5x5 pond full of plants( taro, hyacith, canna, watercress, cat tails, and others) that then makes a waterfall into my main pond. The water comes out crystal clear.
WJ

Thanks for the help and suggestions and ideas. I read a lot of the other postings and realized that a bog garden is mostly a separate entity than a pond. ( Now I Want A Bog Garden ) I appreciate the help. insan/jjl

are those primroses you have around the pond or some variation? if so i am jealous, i had a potted primrose that i could not plant immediatly (because of harsh frost) that died almost the day i got it