Hi;

Welcome to MAAST. Probably 8-12 fish of any species is too much for a 20 gallon tank. As far as lighting goes, 2 55W (65W) P.C. tubes would probably do well. There's an online company, ahsupply, that specializes in PC lighting and can supply the stuff you need. A MH bulb, I guess you would get a single 175, would light the tank well also, but you'd have to solve the heat issue.

You can't have a fully functioning deep sand bed in this size tank. There's certainly no harm in having a sand bed, but you won't get sufficient diversity in the micro-life to process nitrate.

HTH
Matt