ok my tank is now set up, it is 24g, has 6 kg of live rock, the sg is 1.024, the rocks been in for a week tomorrow and as of yesterday ph-8.4, no2-0.5 no3-5ppm nh3/nh4-0.25 alkalinity- 1.3 temp-24degrees celcius i am doing 10%water changes every 7 days (so the first will be tomorrow). anyway according to the literature i have this is all acceptable and expected in the first week. on my live rock and some of the gravel there is a brown matter build up, it comes off easily when prodded and the tank smells fine, so my questions are 1)is this all normal 2)when should i be thinking of investing in a clean up crew and what do you all recomend? i was thinking of some kind of crustacean, or gastropod or maybe a bit of both. oh and the filter media includes activated carbon, 3 filter sponges, a wad of filter wool and ceramic bio rings, plus those plastic thingies that sit in the ack of the tank and are spheres. my pump turns the water 12-14 times per hour. the light is generally on 8 hours a day. thanks for your help craig.