Hmmm, I'm not sure about a single Aurora Puck. If you look at the first posting, you can see how I placed mine. Not that mine are correct, but based off of Rapid LED's recommendation, I needed 8 Pucks. Spacing them as evenly as I could, they are 12" in from the ends, and then spaced 24" apart. I'll attach my plans and hopefully you can see what I did. In your situation, I wouldn't be concerned with penetration in the least bit, the Aurora's are very bright. I'm more concerned about a single puck's spread on your 24" width measurement. Two pucks may be best. Then again, your depth may allow you to use their "Wide Degree" lens instead and a single puck. I used their standard, which is around 90 (they are actually Ecotech), so that I could get the penetration on a 36" tank depth. With the Wide Degree lens you may have to keep the fixture closer to the water. If you hop on Rapid's site, they have a chat window available. Oftentimes Mike or Vince chime in and will answer questions. Give them your tank's dimensions and have them make a recommendation.