Angels would be comfortable from 75F middle about 25.5C to 82F.
Goldfish can live in ponds over the winter where there is partial freezing! A Comet GF can get 18 inches -45 cm! Those can get to be 10 pounds or 4.5kg!!!
They prefer water temp around 65-75F / 18-23C.
If you have air conditioning in the house the fish might get cold even if you live in the tropics. Or maybe in the coldest parts of the year.
True enough about them needing to adapt. If they happen to be bred in your tropical location from a breeder, rather than being shipped in from out of your country / area, they would likely be already used to this type environment.
Gold fish and Koi would like shade or to be in a cool area, sometimes people put fans blowing across the water to help cool it. If you have a light maybe reduce the time it is on/ heating the water.
The warmer the GF /Koi are, the more it shortens their lifespan because it increases their metabolism. Also they will benefit from additional water agitation/ air bubblers so they can get more oxygen, the warmer it is, the less O2 is in the water so they need more available to be comfortable as possible. They don't need strong water current but do need more O2.
If the GF /Koi don't do well over time (they can live 20-40 years) it maybe good to make a different fish selection.
check this out!
http://www.aquariumadvice.com/forum...uire-big-tanks-visual-perspective-265871.html