I saw a pet shop once that made a multi-stage all-in-one filter out of big 30 gallon Rubbermaid boxes, stacked on a wooden frame (top level was five feet or more up!), with many finger-sized holes drilled in the bottom. Top level was a heck of a mechanical filter, next 2 levels were trickle media, and bottom level (a bigger Rubbermaid) was the sump. Next step was a massive protein skimmer (looked name brand) and UV
sterilizer. I dunno how many gallons this system maintained since it didn't look plumbed to run them all. Pretty schnazzy! I wish I had a pic.
I'm leaning on a design that I ran across for CO2
reactors. Cut the bottom out of 2 soda bottles (2 liter), and fill it with the desired mechanical media (dry). smear the outer edge of one bottle with a good silicone bead, and slide the other inside it. Be sure to get a good, good seal. """Engineer""" a tube fitting to each soda bottle top, and find someway to hang the hideous thing behind your tank, out of view so nobody shoots it for pity. When time to clean, hack out the media, clean it, use new bottles, and start over. If I get it done, I'll try to photo it.