Chiller Size Recommendation?

[Aspect]

Needing advice from those with chiller knowledge, currently my tank runs 76-78, but will be needing to drop that to 72-74 in the future. Tank is 400 gallons, I'm wondering if a 1/2 HP chiller would work, or if I'd need to have a 1 HP model.

 

[theMeat]

Check this out

https://www.hamzasreef.com/Contents/Calculators/HeaterChillerSizing.php