I have a 55 gal with 25 lbs of live rock. The tank is new. (2 weeks) I also have 2 yellow tail damsels and 2 green chromus. I found a guy in the paper selling his tank and access. He has had live rock in his established tank for about a year. I'm thinking of buying 30 lbs of his rock. Do you think it will be ok to add this directly to my tank now? Will it kill my fish? Thanks for any suggestions.