The tank coolers that are small fans that blow air over the top of the tank only reduce the temperature by 1 or 2C. A normal fan that you would use to cool yourself down with, is cheap and does the same job.
You can buy aquarium chiller units that are refrigerated units connected to the aquarium by hoses. Water is pumped from the aquarium, through the chiller unit and back into the tank. It is cooled in the chiller unit.
Aquarium chillers are expensive and normally keep the water too cold for tropical fish. However, some are better than others and can cover a wider range of temperatures.
The best value for money is a portable room air conditioner that keeps the aquarium and you and your family cool. Portable room air conditioners cost about the same or sometimes less than an aquarium chiller unit and cool the tank and entire room down. An aquarium chiller unit only does the fish tank.
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In Australia, we try to have air conditioning on newer houses but not all have them. Reverse cycle air conditioners are common now because they warm in winter and cool in summer. Most of our houses are poorly insulated even though there are building codes saying all new houses must have some roof insulation. My place is 3 years old and doesn't so developers and home owners are breaking laws. Most houses here don't have double glazed windows either and virtually none have wall insulation or floor insulation.
In the UK and most of the cooler parts of Europe and America, houses have very good insulation and if you can cool the house down, the insulation should help keep it cool and stop the air temperature and aquarium water temperature from getting too high.
A portable room air conditioner (either a standard refrigerated unit or a reverse cycle type or an evaporative cooler) would all help cool the inside of your place down and help keep the tank cooler.