ideal nano size

[Delphinus]

I really like my 20g (well, sometimes, anyways .... the times I don't like it, it's not the size that bothers me, but the way that I've set it up that bothers me -- I've learned so much since the time I set that thing up ... I really didn't know what I was doing). The dimensions of a 20g give several options. It is also, IMO, an ideal footprint size to be lit by a single metal halide bulb.

That said, I don't know if a 20g really qualifies as a "nano." "Mini" maybe ... but not really "nano."

I'd love to try doing some kind of reef with an unused 5g that I have sitting around. The problem is, most things that I have an interest in, tend to get large, and it wouldn't take too long to overcrowd a 5g. I don't even know what kind of fish I could keep in that thing. Juvenile fish maybe ... but it seems to me most things would outgrow it in a matter of months?