Going to be kind of hard to work on/service. With the sand and everything in there, you won't be able to pull the plumbing apart to clean or change it. Also, my concern would be having all that stuff so close to the overflow drain input. I would think you would end up with more sand and stuff going into your sump and therefore into your return pump which shortens the life of the pump. I think it would be best to try it without the sand if you do it. The cheato just needs light and the nutrients it absorbs from the water. Still you would run the risk of clogging your overflow drain pipe and flooding your tank. Even if you covered the intake with some filter floss to keep the cheato from getting intot it, you would have to change it very routinely to keep it from getting clogged up. If it doesn't completely clog it, it could slow the drain down just enough to where the pump is feeding water faster than it is draining into the sump and you could overflow the tank.