Most killie keepers that are in the NZKA have a range of tanks.
My main setup is 200 x 200 x 300mm.
Lots of them.
The only air going into them is an airstone or a bubbling length of air-line.
Water changes are relied on instead of filtration.
This size tank can present itself as a cupboard fishroom system, heated with only a light bulb and controled with a thermosat.
Other tanks are up to the 600 x 300 x 300mm.
For the fry anything goes that will hold water.
We also keep our species separate from one another due to the fact that the various females are almost impossible to identify with others of the same type. Between Erling, Tim, abd myself, we would have over 50 tanks, probably well on the way to 100, and that's just the ones I really know about.