id do a penguin 350 hob with a powerhead. put them on the flanks- use a powerhead with a sponge attachment (aquaclear is best) to flow water to the penguin's intake where it will then be purified and then flow back into the tank on the back wall. the water will then flow into the powerhead. this way, you have circulation and filtration all at once.
i have a 29 setup. due to the tank's weight when 90% full, i had to butt it against the wall, so could not do a hob filter. a canister filter was an option, but too expensive for me. so, i bought a whisper 40i internal filter (20 bucks at petsmart) and put it on one end and then put an aquaclear powerhead with sponge filter attachment on the other end. water is crystal clear and both do a fantastic job. i syphon like zero leftover food from the bottom.
thats my two cents.