Cherub Anglefish?

[Macscale]

Hey everyone!
I've been seeing a lot of people say the keep a cherub angelfish in a 20g tank? Is this good for the fish? How do they do it? I always thought that Pygmy angels needed at least a 30.
Is there an exception with this guy? Liveaquaria says 55g...
I know dwarfs need at least a 40 right?

 

[aumholdings]

I love those fish!

 

[Flaxon-Waxon]

I just added one to my 40 breeder... I dunno how good I'd feel about having one in a 20... They do like a lot of rock work with hiding places.