Here's another idea for decorating a tank. I've never done this before but it really looks great, especially with betta tanks. Its the ideal solution for smaller tanks with low lighting, or owners that don't want to deal with the hassle of caring for live plants. I want to try it out, but my betta boy would be all pouty for sure if I took out his tree trunk cave.
You can create your own surreal floral garden in the fish tank. Select colors that look good together and also compliment the color of your fish. Avoid colors that are the same or too similar as the fish color. Silk flowers are available at all craft stores, and are perfectly safe to use as long as it is all SILK. Don't buy the shiny plastic kinds, or flowers dusted with anything. Make sure there are no protruding wires too. You can also buy silk greenery for compliments, or you could do all silk plants instead of flowers (easier with a larger tank). Silk craft plants come in all sizes and shapes, and generally look less fake than the ones I've seen at the store.
After you bring them home, cut the stems to the desired lengths and put a dab of aquarium sealant at the cut end. That way if there is wire inside, water can't reach the metal and the metal can't reach the water. It helps to use the sealant to glue them to something to keep them down and secure. Let it cure for a week and its ready to go in.
Here's a photo of my flower/stone tank. Stormy and I both love it http://www.timstropicals.com/photopo...to=612&cat=579