Basically it won't be able to skim the tank volume fast enough to keep the disolved organic's at a low level, defeating the purpose of having a skimmer. It's efficiency will drop dramatically if placed in a larger tank then it was designed for-it won't produce MORE skimmate to make up for the larger water volume. I hope that made sense LOL
. My 2 cents-Don't skimp on a skimmer. I spent about $100 on "cheap" skimmers before finally getting an aqua-c. I could have saved money and "headaches" by just getting the aqua-c to begin with, there is no comparison among other HOBs.