20g....uhmmmm

[skinless]

remember the differences between male and female cons appearances is impressive too.

 

[Kuda]

id say a pair of cons would be nice, there plenty agressive, expessially when they start breeding, but theres really no monster you can fit in a 20

 

[mickey85]

I'd also vote for a leaf fish. YOu could make it the ultimate biotope aquarium, and how badass is a fish that will eat something 2/3 its length in one gulp? Just got one today for my 20G...

 

[guppy]

Because of it's habits even the largest leaffish (Nandus nandus) can work in a 20g and they are cool, I don't know about legality in Hawaii though
Maybe 1 Aholehole (Kuhlia xenura) they get to 9" and can be kept with a teaspoon of salt per gallon and are Hawaiian natives.

 

[Masterchief]

A group of neon tetras and a pleco, theyr`e not completely monsters but they make a good combination.

 

[limz_777]

snakeheads