This all depends on where you live and your climate. Most reefer homes are air conditioned or usually stay cool throughout the day. HOWEVER..... Chillers are great....for your size tank anywhere around 1/4hp should be able to handle that amount of water.
I personally own a JBJ Chiller and it seems to be a fairly reputable company. And there are others as well. I'd say try the forums for a used chiller just to save on the cost...plus you may be doing someone a favor/vice versa.
Most chillers require a certain amount of flow to properly operate...approx. 400 to 700gph flow.
What is your current tank temperature? And where do you live as far as climate? What types of livestock do you have?