Awesome picture zaraemna...that is a beautiful specimen! That is my favorite sponge.
It's commonly called a Blue Tubular Sponge. I've seen them sold/labeled by the scientific name Haliclona sp. (like PSam mentioned), and Adocia sp. It's hard to truly identify sponges positively without looking at their tissue through a microscope though.
Like uhuru mentioned those blue tubular sponges tend to be photosynthetic, so lighting would be recommended....as well as the disolved organics and bacteria. I keep alot of sponges in my tank and stir my shallow sand bed up a few times a week to help them out.
Keep in mind those blue tubular sponges tend to be toxic as well if they die. I had a specimen die off on me rather quickly, and it affected my tank inhabitants. Got one in a shipment that had white patches on it, and tried to save it so I put it in the tank anyway. Big mistake cause it continued to decline (probably had air trapped in it) and poisoned my tank.
I was fortunate enough to catch it in time, and was able to do water changes and run alot of carbon to counteract the damage done. I clipped a few of the living pieces of blue sponge and planted them in my tank as frags. Luckily some took, and I have them, but their growth is slow unfortunately IME. I've read from others that they grow quick in low flow, but my tank for the most part is high flow. Maybe that is why mine grow so slow.
Good luck with it...it's a beauty! :thumbsup: