well the difference between a sand bed and no sand bed in a large tank is huge. I will never ever ever put sand in a large tank again after going BB on my 75g. I then took the sand out of my 2x 20g, 40, and 90 and the paramaters of the tanks are so much better and I dont need to do weekly water changes to keep my nitrates below 5ppm. However I was thinking that in a nano the tank may be better off with sand just for looks and for the simple fact that I am not worried to much about a sandbed in a 4g tank. There will be no fish in this tank I dont think. I am probably just going to sport some Sexy shrimp. MAYBE a neon goby at some point but im not sure if i want the waste that one will produce.