Unlike tanks with a substrate, you will need to siphon detritus and wipe away algae weekly. You will have less light reflection, there will be nowhere for gobies, shrimp and wrasse to live, you will have less dentrification capacity and biodiversity. If you have no substrate or remote sand bed, you will not be able to achieve a higher order ecosystem.
If you're still sold on a bare bottom tank, you can minimize detrital settling by installing a closed loop that projects flow across the substrate in a circular motion (end to end). The flow dynamics should be set-up to move that water to the surface and across to the overflow box. Avoid directing water in the opposite direction of the overflow. at the surface. You should also have several mechanical filters in your overflow and sump. These should be rinsed or disposed of daily.
You would also have better success if your rock work was supported by a minimized base. This will allow water flow and siphon access. Snails, shrimp, urchins and serpent stars would be the best cleaners. Hermit crabs should be excluded, as they will kill your snails and assume their identity.