Hi, My husband bought his first marine tank at the weekend. He has so far put in his sand and a packet of broken rocks on the bottom, filled it and put the salt in. This was done on Sunday. He is now taking readings with his hydrometer and find that it is giving him different readings every time he does a test. His next step is to put in the live rock which he will hopefully do this weekend. Can anybody tell me where the best place is to go for this.