Listen emilio you basically can do what ever you want with your tank there are many people who do similar things. However a Zebrasoma sp. of any type, yellow tang included, needs to have a large area to live. I'll put it like this: a dog can live in a 5 foot bye five foot cage and maybe could live for a long time like this however just because it is possible doesn't mean it is the right thing to do. Also it will inevitably lay in its own excriment from time to time. With this said just know that this is going to be possible but it borders on abuse. Again i am not trying to be rude i am just letting you know. The site that you have saying that a tang can live in a twenty gallon tank is of course a pet store who makes their living on the fact that they can convince people much like yourself who do not do enough research and prematurly buy a fish like this.
Just so you know a nano tank is for a small reef community maybe a few coral and a couple catalina gobies, get your self a harliquen shrimp if the mood strikes you but not a tang. My advice is to take you existing tank and turn it into a sump for you new tank.
Just so you know a nano tank is for a small reef community maybe a few coral and a couple catalina gobies, get your self a harliquen shrimp if the mood strikes you but not a tang. My advice is to take you existing tank and turn it into a sump for you new tank.