Undergravel and sand help?

From my knowledge sand doesn't work with under gravel filters if you are trying to do it that way? If half is sand and half is gravel you could easily use the under gravel filter on the half with sand and it would work perfectly fine. I personally like under gravel filters on smaller tanks which can be gravel vac'ed easily with minimal time. They work just fine but you do need to make sure there's a thick enough layer of gravel to ensure to poop gets under the plate or a toxic build up can occur. I use 3-4 inches in my 20 longs and it works great. Along with weekly maintiance and a back flash once a month with a power head it's just as good as any filtration but a bit more tedious to maintain.