Because of the very narrow confines of the five hex, you won't have happy fishies. They'll be bashing themselves around trying to swim and having no where to swim too. Also, because the five is very tall, you have to worry about lack of O2 and circulation at the bottom of your tank, espeically for bottom dwellers who may not take too kindly to suffocating in heavy ammonia water. The hex shape has a tendacy to distort the look and view of your fish because of the refraction, your fish may look cut in half or some other weird shape. The narrow bottom allows for less fit of decorations.
Those are just the disadvantages of hex tanks in general, no matter what size.
As far as the filtration goes, I believe it is the same model filter they use on their three and two gallon tanks. Hmm...how can a filter that is rated for two and three gallons be as effiecent on a five gallon tank? That's just food for thought. But the Marineland products themselves are very reliable products, so I wouldn't have anything against the filter itself. As far as I can tell, nothing extra is in the six except for the filter that operates on six gallons being bigger, and for the extra volume.
I have an Eclipse system 6 at home, and I enjoy it. It doesn't take up as much space as the five does because it's not as tall, especialy since I have it on the bottom shelf of an already existing tank stand (that has my 20g on top). I've got a pretty decent size rock in it, a replica resin sunken tree stump, and a whole slew of plastic plants. I've had it running over a year now, and so far, I've no complaints. Well, except when the snails climb up into the filter and block the biowheel spinning.
But if your tastes pull you towards getting the hex, then go for it. Being that they're both Marineland products, I'm sure they're both equally good.
~~Colesea
