The info provided says 30" X 31" footprint, not 30" X 15". That's actually a larger footprint then 48" X 18".
Very questionable wether the bent backs of some JD's is due to them being kept in small tanks. I've seen JD in the past with bent backs that were kept and raised in large tanks. The thought of many, is that a bent back is related to nutritional defecientcies. The poor genetics of mass produced JD as well as WATER QUALITY. There is eveidence from aquaculture that water quality can have something to do with nutrient absorption and thus is connected to nutritional defeciencies. So I guess in a round about way, If a small tank means poor water quality, (and you happen to get a JD genetically inclined to get a nutritional defeciency), then I guess you can blame the small tank for the bent back.
IMO, you can always more then make up for a lack of filtration with more water change, but you can never make up for a lack of water change with more filtration. As long as you have suffecient biological filtration, then it will be fine and since your going with 2 sponge filters both rated for tanks double the size of yours, i really can't see how you could have a problem with it.
