Just in case anyone is interested, I'm posting the emails to/from AquaEuro. Have not yet heard back from Hydrofarm...
I asked: "I wanted to use your 1/13 hp chiller for a planted freshwater aquarium. I would operate at a flow rate significantly under the min flow rate recommended. Is that not a good idea?"
They responded: "I would not recommend purchasing our chiller in that event. It must be operated at the correct flow rate requirements otherwise it either wont work for you or it will freeze up and damage the compressor. Sorry but it must be used in those parameters."
I then asked: "One follow up question. What is the minimum flow rate for the 1/13 hp chiller? I see 50gph listed in the product manual, but I see minimum recommend flow rate of 160 gph in the product descriptions on most websites. I could run my tank in the 50 gph range, but not at the 160gph range."
They then answered: "At 50 gph, your pump has to be right next to the chiller itself. It is too slow of a flow rate. It should be 160 gph."