I found an 180 gal tank 6'x2'x2' for $550 is this a good deal or should I stick to the 120 gal for $384 I found? Also I would like to put more fish with my 15 inch alligator gar that I have in my new tank ^ which I still need to decide on, but I love Dats and I want some of those how many should I get if I were to add another gar also?