Quick Question On Live Sand

[black molly3]

would arogonite sand and live rock be ok in the dark for a few days because when i go i am taking my tropical fish back this should give me 15 pounds worth of credit. then i have 10 pound or 15 pound extra i will use this to get sand or mebee some mor live rock. or could i get an 18 inch 60/70 watt light for this price.
thanks