Which urchins?

[DJREEF]

Hey Doc,

Welcome back. Quick quiz for you. Which species' of urchin do you recommend for hair algae control? I currently have 4 Mespilia globulis in my system, but all they seem to eat is coralline algae. This isn't a prob cause I dig the way they look, but they aren't interested at all in the few patches of hair algae that I have. Just looking for some more 'non-tang' options.

Thanx Doc,

DJ

[rshimek]

DJ,

I suspect the best option will be a long-spined urchin, an individual of one of the several species of Diadema.

I think also another option would be to cultivate some macroalgae to outcompete the hair algae for nutrients.

[DJREEF]

Thanx for the genus recommendation Doc,
I'm currently working on getting a gravity fed 45 gallon eelgrass bed together as we speak.

DJ

[moses]

Hey Dr Ron/All

The long black spined urchins may be great for algae control, but aren't they bulldozers and will ***** your corals in the process of getting to the algae.

What about the royal urchins, these guys have much smaller spines (1/4" at max) and bodies too. The LFS says they are reef-safe, but I thought all urchins ate sponges so the term reef-safe should be used with tongue in cheek.

I believe these guys go by another common name of Tuxedo urchins. I don't know their name taxonomically speaking though.

What do you think about these guys, Dr. Ron

[rshimek]

moses,

Here is an article on urchins for your perusal...

http://www.animalnetwork.com/fish2/aqfm/1999/june/wb/default.asp

Almost no urchins eat sponges.

Tuxedo urchins are discussed in the article. Their primary diet is coralline algae and they will give the coralline in a tank a nice natural look. However, they don't do a lot of grazing on many other types algae. I have had them eat hair algae occasionally in my systems.

Diadema may be bulldozers on occasion. It is the luck of the draw....

[moses]

Hey Dr. Ron

I read your article. Thanks. Ummm.. one interesting note I will add from reading your article is that you mentioned that: Eucidaris tribuloides, Common Caribbean Pencil urchins, do eat soft corals, sponges and shrimps. That's what gets me anxious every time I see somebody advertising an urchin as being reef-safe.

But according to your article and the implications of your post below, my open wells brain, favite brain, and nameless hitch-hiking sponges will be safe with a tuxedo urchin, which I eyed at the LFS store yesterday.

[rshimek]

Originally posted by moses
. Ummm.. one interesting note I will add from reading your article is that you mentioned that:Eucidaris tribuloides, Common Caribbean Pencil urchins, do eat soft corals, sponges and shrimps....

Yes, indeedy. But pencil urchins are the only generally carnivorous urchins. Others will occasionally eat pieces of food or the wayward angelfish, but seldom will touch sponges as sponges are generally exceptionally toxic.

Pencil urchins are relatively rare in terms of species number, so when I referred to "almost no urchins eating sponges" I was considering pencil urchins as group (cidaroid urchins) as being relatively rare.

Tuxedo urchins are pretty much safe with all animals.

[original-reefland]

Ron,

I'm interested in a long spined urchin but I have concerns for my anemone and LPS corals. Not that the urchin will eat them, but that the long spines will tear them apart.

And secondly, do urchins tend to ignore each other? same species or not? I have a blue tuxedo, and I'm wondering about any interactions of introducing another one or introducing a different species such as a long spined.

Thanks Ron.

[rshimek]

Originally posted by original-reefland
Not that the urchin will eat them, but that the long spines will tear them apart.

These animals coexist in nature without entanglements, and they will do equally well in our systems. I view this as a non-problem.

And secondly, do urchins tend to ignore each other? same species or not? I have a blue tuxedo, and I'm wondering about any interactions of introducing another one or introducing a different species such as a long spined.

They probably will not interact at all. Urchin-urchin interactions seem to more limited to shoving matches than anything else.

As long as there is food for both, I see no reason not to have both in a tank.