Are you talking a sand type filter? If so then that would be perfect. I use a gravity style filter setup, where my pump is a pond pump in the tank and then the water is pumped up into the filter and then the water just drains back into the bait tank.
I resessed the pump into one of the slots in the bottom of the hazmat spill container, then made a metal plate and drilled holes in it for the intake, then I used 5200 marine/rv adhesive/sealant to stick the metal plate down.
This is my filter, its a 39 gallon construction tote/garbage bin that I turned into a gravity filter. inside is a spray bar, which then sprays onto differant grades of HVAC filter material, then in the bottom is a bunch of bio balls, cut offs of pvc pipe, Light diffuser panels, and plastic banding from the lumber yard. There is a shower drain in the side to allow the water to flow out.
you could use a 5gallon bucket suspended over the tank and holes drilled in the bottom to drain back into the tank. There are a ton of ideas on iceshanty. This was just my approach/version of a gravity feed filter. It worked really well for me, I had a ton of bait in it, large suckers, med suckers, golden shiners. Only had a couple die off, but that was due to the crazy warm weather.
I run a 1200gph pond pump
