Bigger the better, they like being social in groups. While demanding high water quality. Basil knows his stuff and I echo his view, that 60l is much better than 30l.
Although I keep CRS in an ADA mini M, I maybe change water 2-3 times per week and check daily. I would prefer a larger tank for them though.
It's all dependant on how much time you have to play about and check everything is ok.