Ok, that's good to know. I haven't encountered a 9 but I have some 7's, a 12 and 24, had a 18. It definitely isn't a 12 or anywhere close, so it can't be a 9. Its size is really close to a 7 and from the size of the tank, I would say that it can't be a 5 or smaller. From the tank's requirements, I would have put my money on it not being a 7.
...looks like shifting gears would be a good thing.