All good ideas. I would suggest bare bottom tank as a choice for sure, and make sure to use lots of marine pure spheres in the sump. I would use Dr time nitrifying bacteria to quick cycle the tank because it has the most nitrifying slow growing bacteria in it. As far as the rock, Only use dried bleached/ rodi cured coral. Coral is made from calcium and is a buffer. Dont use any of tbe imitation concreted real reef style live rock because it comes with bryopsis and possible hitchhikers. Speaking from experience. -Bare bottom -marine pure spheres in sump -double dose of Dr Tim's nitrifying bacteria -only God created coral rock dead/cured. If you go with sand I recommend using a number 3 sand which is coarse enough to avoid dust/sand storms and is really easy to sophon/clean without losing sand and causing sand/ sludge storms. It's also still friendly/small enough for your goby. I also prescreen the sand to get rid of the contamination of fines and rinse it well to get out the plastic and floaties.