I tried to make my own cannister filter. Basically the 5 gallon bucket with a gamma seal lid as demonstrated the King of DIY.
My attempt failed miserably. While I could get it to work, without leaks, when I tested it with the power off (simulating a power failure) the siphon would have enough pressure to create a leak around the gamma seal lid. No amount of fiddling, Vaseline, new/extra O-rings, or silicone sealant could fix this. What I realized is that King Joey's bucket cannister was at the same level as the aquarium (hence no automatic siphon when power is off). My cannister bucket was positioned below the aquarium in stand. So, 5 gallon bucket cannister was a bust.
What I finally did was to create a cannister out of 6 inch PVC pipe, with a sealed end cap on one end and a screw-off access cap on the other. Since this is real pipe, and originally intended for sewage, there was no leakage on the PVC end. The inflow and outflow pipes required a little fiddling. A uniseal worked for prevent leaks at the inflow connection, but a regular pipe bulkhead was needed for the outflow pipe. I went with an external pump, so there was no need to seal a hole for the electric cord. Flow goes from one end of the pipe cannister to the other. The pipe is mostly filled with lava rock and bio balls, but there are some sponges and a little bit of floss on the screw-cap inflow end.
I now have a working DIY cannister filter. It's main headache is priming it when I need to restart the system. I learned that adding a small air hose valve on what is the high end of the cannister helps a lot. But, put a small ring of large open pipe around the valve to guard against knocking it off an breaking it (I think I did that three times before I learned to protect the valve).
While I learned several things in the DIY process, my biggest lesson is that DIY is not necessarily the least expensive alternative. I think I ended up spending close to $500 on this project. I could have gotten myself a damn good Fluval cannister filter, and a couple of cases of beer, for that price.