DAS internal overflow thing...

[Yano]

I have this acrylic DAS thing(17.5in x 4in x 22in) that the person I bought my new tank from threw in for free. It has a skimmer in it, is this worth using? Where can I find some info on these things? It has an overflow thing and several chambers(Some of these seem like they go no where/ useless, but what do I know). I googled it, but did not find much, most was not in English.