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I second that Koralia 240 that autumn mentioned above.
For a reef, depending on what if any filter you are using you may actually need two, one for each side if you are keeping coral.
But yeah, figure about $20-25 for a powerhead. Don;t skimp out and get the uber cheap ones off ebay, I had one explode and leaked oil out. Luckily it was just in my mixing can or the results could have been very, very bad.