Udotea or mermaids tail coraline algae.

These are directly related to the halimeda, making it a flexible form of coralline algae.

The udotea are of the order caulerpales and from the family Udoteaceae which includes many species.
They are found in mud flats in massive numbers and have a bulbus end to the trunk that penetrates the substrate and at times, this base attaches to a piece of rock or dead coral under the substrate.
The bulb holds it in place by the suction affect of a larger object beneath the mud, enabling it to remain in place in at times in quite rough conditions.

These algae will take on a multitude of shapes and sizes to a max of 8 inches across the fan shape to it.
It can be found with multiple fans from the one trunk and will grow multiple fans from the original once in an aquarium.

They require the same dosing needs as corals and require low to medium lighting.
You can attach a small piece of rock or dead coral by stitching threw the bulb on its end and tie it to the rock/coral piece so it does not get blown over in the aquarium by wave maker currents.

If collecting these it is important to dig down beside them to make sure when you pull them out, the bulb is not damaged.
These are a very easy to keep and an attractive reef aquarium addition.

In this area of mud and algae there are thousands of the mermaids tails, usually partly covered in other algae.


A closer view


An even closer view


In the mud




Bulb with a small rock attached.


Just the bulb.


There are a few udotea in this pic to show how many variations there can be to the mermaids tail.