Be aware that as you keep small size fish in your 29gal (zebra danios), the suction power of the intake could trap them, injuring or even killing the fish. Using a pre-filter sponge seems like a good idea if you intend to keep small fish there.
I love the AquaClear 70. I run two 30gal wide tanks with them as primary filtration. Their performance is quite impressive despite the old technology in them. Keeping the inlet close to the substrate improves their mechanical filtration as this ease the pick up of solid waste but if you are keeping small or mid size fish that are not messy this might not be needed and keeping the inlet at midpoint shall suffice. This filters, if properly maintained, do catch up (allow beneficial bacteria to grow) quickly as
bio-load is increased.
Pepe
Santo Domingo