Get some 20 gallon BRUTE tubs at Lowe's. All Rubbermaid BRUTE products are food grade so they won't leach. You need to use saltwater to cure the sand. You don't need a powerhead, but a small heater will help (unless you keep area the with the tubs warm). You do need to stir the sand every couple of days. Don't put the sand more than 2" - 3" deep in a tub.
Wet/Dry systems are FAR from the best filtration, unless you want a Fish Only, or a FO
with some LR
tank. A wet dry completes 2 of the three stages of the nitrogen cycle. It is very good at converting ammonia to nitrite and nitrite to nitrate. Hence its reputation as a nitrate factory.
If you want corals, or are lazy about partial water changes a wet/dry cannot compete with LR
(1.5 - 2 pounds/gallon) along with a good skimmer. Add a DSB
(deep sand bed [>4"]) and a refugium with some macro algae and you have a natural system that takes care of the complete nitrogen cycle.