what air temp is it in your house?
Right now 21°C.
Good work EK. Like yourself IM not paying to heat the house THEN to heat fish tanks.
Just think practical...
My fish are fit and healthy. There are people that think that I'm neglecting my fish by not using heaters and don't have temperatures between 24°C - 28°C. In my opinion, those people just don't know what they're talking about. Most people just focus on the word "tropical". But not every socalled tropical specimen needs high temperatures to keep them well and get them to reproduce. You need to know where they come from. And I don't mean the country right away. But more the area within that specific country to understand what they really need. Firstly, every tropical and subtropical fish has got a margin that they tolerate in temperature. And does a fish originate from a subclimate that's subtropical within a tropical zone? For a lot people don't take that in consideration.
If my fish are in (no matter which species) a poor condition, the way I'm keeping them, I'd gladly invite one over to see that those fish are in a good condition. For I can prove the opposite. I even have an official health certificate hanging in my fishroom. I can be checked randomly in person by this official organization. They'll check if I maintain the fish in the right conditions. Those fish will be checked on bacteria, parasites and illnesses. And the water parameters will be checked.
So yes, I'm a serious hobby breeder which also uses an official organization to back me up. They do know that in general I'm not using the rules of the holiness of the aquarium book. But they also know that my way of maintenance works.