it is.. lemme see if I can find a few pictures from the old tank..oh show's you my lack of knowledge thought it was a a support to set the plants in the tank, placed a ivy vine in my tank yesterday hope it takes root.
hmm seems they've been deleted. At any rate, it is used as a support for plants. It is a square grid made of plastic. It's original use is as a light diffuser however we aquariasts repurpose it for all sorts of things.. I cut a length of it that went from one end of my tank to the other and was about 4 inches wide. i then fed the roots through the holes and let them sit in the water while the plant stayed out. It works, I'm not a big fan of massive dangling roots in the tank though.