From another comment here: "you need to be able to keep the water below 24 Deg C, this means spending some money on chillers even in sub-tropical countries"
I think people anticipate needing heaters for certain types of fish, but I'd never have expected to buy a cooling unit for aquatic life.
Yeah, adding in a chiller makes things way more complicated than just adding a resistive heater. A decent looking chiller for an aquarium is ~$1,000, plus you need temp sensors and control wiring to maintain the setpoint properly, and then you need to pray the electricity doesn’t go out. A 1/3rd HP chiller draws around 1kW including the circ pump
An aquarium backup battery for a simple pump is like $50 for something that'll last a few hours of outage, but for a chiller with that kind of draw, it's a bit more expensive.
I think people anticipate needing heaters for certain types of fish, but I'd never have expected to buy a cooling unit for aquatic life.