This may have been mentioned already, but I came across this video a couple months ago and just had to give it a try: https://www.youtube.com/watch?v=PMmfM-5ln64 Basically built mine exactly the same way but with fewer fittings (top doesn't need to be sealed) and made my own bulkheads for the overflows using O-rings and PVC electrical fittings. About $15 including Polyfill filter media (be careful to get untreated 100% polyester). Mine is running at a relatively slow ~130gph using a submersible pump I had lying around so it's most effective for biological filtration, though it's as good as a canister at trapping any solids that make it inside. Anyone else done something like this or are most DIY filters wet/dry or canister type? If you have made a DIY HOB filter, how is yours set up? What media do you use? How would you compare it to a store-bought filter?