Nick,

Great looking build, your tank is going to be something to follow.

Based on the specs, the PTC6 is designed for 600 liters or 160 gallons, so 180g is likely not unreasonable, but pushing it perhaps - it will really depend on the differential between the ambient room temperature and the desired temperature of your tank. If your room is a few degrees cooler, I would think that it should be within the capabilities, but if your room is close to the tank's temperature (ie. in the summer), then it's going to be working pretty hard.

My most efficient and economical cooling is the propeller breeze fan... it's tough for anything to beat evaporative cooling. It brings the temperature down about 3C in the summer. Combined with the PTC6, I feel that I have the most efficient and stable temperature possible.

Are you looking to replace your current chiller or supplement it?