HELP needed: Pond filtration & Filter media in Montreal

Hi, I'm new to this pond thing and have had mine built and running for about
4 weeks. Its about 600 gallons. However, when we built it we did not think
about filtration (mech or bio) and now my pond has turned a shade of
brownish red. I think , from what I've read on the internet, that I want a
combo bio/mech filter. I've I looked around and think it will probably be
cheaper to build my own. Here lies my problems.

1) I need a good and simple filter design that I can build myself. I
already have a 1200 gallon/hr pump where about half goes to the waterfall
and the other half back into the pond. I was thinking of taking the non
waterfall output and passing it through a filter. Does anybody have any
good links to possible filter designs.

2) From the designs that I have seen, I am having trouble finding filter
media locally. I live in the Montreal, Canada area and am hoping that some
of you may know of some local dealers that can supply me with what I need.

Thanks in advance guys.

Mike