cone gravity filter

i been thinking about some way to filter out deitris. i used to use socks, but i always caught a bunch of pods and stuff that i wanted to stay in the tank. i would have to try and catch all that i could and throw them back. needless to say, i got tired of messing with that and stopped using them.
i always liked the idea of cone shaped sumps (sorta something like for outside water gardens). the heavy stuff settles to the bottom while clean water flows back to tank. the bottom would have a drain valve so all the settlement could flow out or be pushed out by the water flow. when ever you see any debris, just crack the valve just enough to flush it out. the only problem is i dont know how to diy something like that(being a cone shape). it would have to be large enough to have alot of water flow and still give the settlement time to settle. anybody have any thoughts or ideas?