Good point Doug. I think it would be quite easy infact. I doubt you would need a screen by the inlet as they would only float up the channel if the flow stopped and any screen would catch the crap. You would want to make an adaptor of sorts so channel the water down to the bottom and extend the pipe the answer normally sits on to the top. Nice thing about trying this in a nexsus is if it doesn't work you can put it back like it was and bung the K1 into the filter itself.
Akai-san you mostr definately want to convince Papa-san that a gravel filter is not the way to go.
B.Scott