Stocking ideas that don’t need a heater

[Jacc]

My little brother is setting up a new 55gallon and he wants to stock it with some kind of gourami but we live in Denmark so electricity is not cheap so we can’t have a heater. So do you have any idea for some hours mid that don’t need at heater. Thanks I’m advance.

[Fish Folk]

Hello! I am not certain if I properly understand your question, "do you have any idea for some hours mid that don't need a heater." Maybe there is a typo in your sentence. I'll try to provide one sort of answer . . . 

Tropical fish tend to need temperatures ranging from 21-26 degrees Celsius. But there are temperate fish that can be kept much colder. I am not sure what temperate  species you can find in Denmark, nor what the laws are there regarding keeping them. But you might inquire about minnow species sold at freshwater fishing bait-shops. There are several European minnow species we cannot get over here in the USA called Phoxinus phoxinus (Eurasian Minnow) and Phoxinus dragarum (France renaming). They look quite basic at first, but in breeding season, put on a lot of color...

Phoxinus phoxinus

Phoxinus dragarum

Here is a comparative chart showing a portion of the Phoxinus genus...

Edited November 25, 2022 by Fish Folk

[redfish]

Is the tank going to be inside your house?  If inside the house, what is the temperature of the room with the tank?

Here is a link from Aquarium Co-Op on cold water fish.  I'm not sure if you can get any of these in Denmark but it should help with ideas.

10 Best Coldwater Fish That Don’t Need a Heater

[Expectorating_Aubergine]

If your house has heating, and is comfortable for you, you can have almost any kind of fish. Many fish will be less aggressive and live longer when kept at lower temps than what is typically recommended.