beachcomber

My interest is local cold water marine. I wish to collect specimens myself and need setup guidelines. Have been unable to purchase a book that covers this. Have a tank 1260 long by 400wide by 520 high. Need to know things like can I put sand in the bottom (want to keep some Dosinia anus and paddle crabs to study their interaction) but have been told coarse material is better. Then filtration? have been getting conflicting advise there. I am in the Orewa district north of Auckland, and air temperature is of concern. My house faces north and is very warm. Would be extremely grateful for some advise. Thankyou.