First you need to figure out what kind of reef you are setting up. I'm assuming you are doing low or low-moderate flow corals (ie softies and some LPS
). I've been away from the hobby for quit some time, but low-moderate flow would be around 20-50gph. Well over 50gph would be high flow SPS
2+ powerheads is better than 1. Reason is you help create the right flow for different areas of your tank depending on where the flow is coming. You can set up the flow to make the bottom area of your tank for low flow softies and higher area of the tank moderate flow LPS
This above is the main reason to why powerheads is important to a tank to a reef tank. Other important features is keeping the water going through the live rocks and keeping some debris and waste suspended until it gets to your overflow, filter, or water changes.
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