Does coral float? My brother gave me a big piece of coral but it's floating in my tank.?

Question

Yes, it's dead. It was a big "rock" he found on the beach. I have live rock and it does not float I was just wondering if it is fake coral made of something else.

Answer 1

Coral is calcium carbonate for the most part of it's composition, and that's too dense to float. What you might have is a volcanic rock called pumice which is similar in appearance to coral. This is made of a light colored "lava" in which a lot of bubbles form from volcanic gasses bubbling through. So it's something like "foam" when molten, and it keeps the same texture when it hardens. All the spaces with gasses trapped inside makes this light enough to float.

See photos:

http://www.gc.maricopa.edu/earthsci/imagearchive/floating_pumice_big.jpg

http://www.lcc.ctc.edu/departments/natural_sciences/pictures/archive/im_wk_pics/pb230076pumice.jpg

Answer 2

Dead coral should not float as it is made up of calcium carbonate deposited as a skeleton for the coral polyps.
Take it out and check that is has not got any rotting coral internally which will make it lighter and so float. Gasses collecting in the middle will cause this.

Answer 3

I found a bright yellow rock at the beach today. I think it is a coral ,but it floats

Answer 4

I have never seen Coral float,and we have it all around here, i think you have some fake coral there.

Answer 5

Coral floats once it is dead. Other than that, I have never seen coral float.

Answer 6

I have a heavy 20 pound dense piece of brain coral that I collected from a beach many years ago. I decided it was time it had a bath and in doing so, I discovered it floated! I found this incredible as it is obviously real coral and quite heavy!