because it's a seahorse tank and I find the these wires easier to hold for the seahorses. I'm actually planning on putting 2 more and paint the driftwood green and have orange wires coming from the sides.
I find seahorses don't need large aquariums as they are mostly sessile. During my conversation with a seahorse breeder, he told me about an aquarium that was 10Gallons and the pair inside spawns all the time.
With this said. You need to constantly clean the aquarium(the 10 gal had daily water changes performed). The reason people recommend big aquariums for seahorses is their waste production not their need for space. I think with a 15Gallon and a good skimmer you can do a weekly water change and keep a healthy seahorse pair.