Water Temp For Endlers/guppies

 I'm afraid that bowl isn't really suitable for any fish. 12 litres is very small and the shape makes it unsuitable. Spherical containers like this have a very small amount of water in contact with the air, and as that's where gas exchange takes place it is difficult to get enough oxygen in and carbon dioxide out even with a filter.
Don't forget that even a room that is warm during the day can get quite cold on a winter's night. You could possibly use one of those pads that go underneath a tank as a heater but they can be a bit tricky as they have 2 settings - on and off, no thermostat. A filter wouldn't be a problem as for a tank that size a sponge filter powered by an air pump would work well.
It's the volume (or lack of it) and shape that's the problem. Even fish as small as endlers need something like 40 litres. You could perhaps use it very temporarily as a fry tank for a couple of weeks, but you'd need to cycle the filter first, and keep it running in the main tank when there were no fry in it. And I do mean only a couple of weeks because any fry would get stunted if left in there very long.



It might be possible to do a plant only tank - but you would need to listen to plant experts to see if it is possible. otherwise, all I can suggest is to use it as a mini terrarium for houseplants.

Sorry.