Lighting an Aquarium with PAR instead of Watts
theres the sticky, i guess there isnt a ton of info on CFLs. Looks like 15w or 9w are your best choices. :/
Hopefully someone with experience with a 20l and CFLs will chime in
And for silica sand, you can look at pool stores, or try like home depot/lowes/menards, or maybe even tractor supply co, or walmart.