Best filtration for a 20 gallon?

[Hybridfish7]

What would be the best filtration for a 20 tall with a single a.sajica in it
I certainly don't think a $60 canister for just the one fish is worth it, and since this is a display tank I don't think a sponge would be very visually appealing

 

[Jexnell]

Get a Aquaclear 50, should do the job just fine.

 

[lm26sk]

ac50 or fluval hob would be my choices but any HOB will work .