Under gravel filter to canister

you can use the cannister, but they aren't meant to move water except for within the filter. you will get better flow with a powerhead. I haven't used a canister, but have used a whisper 5 HOB, but switched it to a powerhead.
an UGF pulls detritus down into the gravel, but it's main purpose is biological filtration. I run the UGF for bio and a HOB for fine particulate filtration.

I hooked up an AC110 to a homemade undergravel filter in my 90. It worked good for many years. The intake fits right inside the PVC tubing.

Run it RUGF (reverse) and you'll see better results. All things considered an ac110 and an xp3 run traditionally should be more than enough.

I was having to clean a Fluval 306 every five days in my 55; the sponges were clogging and water flow cut to less than half.
Added a 406 and hooked both intakes to an undergravel filter that I added at the same time. Astounding improvement. The sponges stay clear because of the gravel pre-filtration; the flow stays constant; chemistry numbers stay perfect until a monthly cleaning, which I do mainly just for fun.