18" depth.... 12" cat.... hmmm.... and a year is a long time to build a tank or buy one.. 6 month ago I owned a 10 gallon tank and that's it now 6 months later I own 5 tanks .....and its actually in a 29 gal tank right now. and when it gets a little larger a 55 is its next destination, and then the 135.... how short do you think is a year anyway? and even so it still wont have outgrown the 135 @ 12"