Marine tanks are welcome here, and it is worth being straight with you about one thing: the written guides on this site are still mostly freshwater. The species database does hold a large number of corals and marine fish, and the people here know their tanks — but if you ask something marine and specific, expect answers from members rather than a guide to link you to. That is the current state and it will change. Useful things to include: Salinity, and what you measure it with. A refractometer that has not been calibrated is the single most common source of confusing readings. Tank volume including sump , and how long it has been running. Rock and flow — how much, what kind, and how it is moving. For corals: lighting and its height above the water, plus alkalinity if you track it. One house rule, and it is the only one that matters: answer the question that was asked, and say when you are not sure. A confident wrong answer costs somebody a fish.