I'd add the sand to the refugium but do not rinse it just use it dust and all about 4 inches deep as for the algae No need for it now unless you want to feed it with a plant food unless you used some really nasty L/R not much for the plants to feed on yet . Just like a skimmer on a new system not much for one to skim unless the tank is areally a mess from L/R use. About 2 months after animals are being added is when I'd add the plants and or a skimmer ..
Also what I have found out over the few tanks I have ran fuges on..And if you use a fuge then a skimmer is needed less then with out a fuge . So you may want to hold off longer for the skimmer addition ? Buts thats just me