We have only veggie filters in small ponds that have bottom drains. No
filters. The plant roots make great mechanical filters. We drain the
veggie filters annually. Also, we have a 'deep well' (think old septic
tank) in the middle of the pond. When the koi swim, they stir the muck
and the larger things like pine cones and needles eventually go into it.
Once a year, I clean it with a swimming pool net.

The rule of thumb is 10% of the surface area of the pond for the veggie
filter. you are close. Does the bulkhead pull from the side or the
bottom? If the side, you will still have to deal with solids that fall
in the pond.

Good luck.

Jim

Lar wrote:
Have a new 275 gallon pond where I have the pump, pump through a
bulkhead in a 25 gallon tub..where I have an A/C filtering material at
the bottom of the tub and above the bulkhead...above the filtering
material I have the plants at different levels in the water...no soil,
then the water spills over on to a small waterfall. Will this suffice or
will it depend on the plants or will a layer of soil and gravel creating
a bog be better for the filter. TIA

a pic is at
http://arrow-pestcontrol.com/100_7258.JPG