Conch update and Diadema question

[ChrisM]

Hi Ron,

A few weeks ago I posted about a Fighting Conch that had been buried for several months. I moved him to a spot where I can observe him better. He is eating, but only what's immediately around him. I guess he doesn't need to eat a lot, since he's inactive.

Also I purchased what I believe to be a Diadema setosum urchin. I'm just guessing on species. Anyway I got it to control algae, but it seems to be more carnivorous than herbivorous. It seems to have developed a taste for encrusting sponges, and on several occasions it raided my E. quad and stole krill from it. In fact I think it may have killed my BTA by poking holes in it while trying to get the food. When it's not eating animal tissue it's eating coralline algae. Needless to say it hasn't done much to alleviate my algal problems. Is this normal behavior for Diadema species, or is this something else to add to my growing list of defective animals? Are there carnivorous Diadema look a likes? Let me give you a description of it, maybe I've misidentified it. This urchin is black with long thin black spines, that hurt like a so and so. It has iridescent blue spots that run longitudinally along it's body, and the anal cone has a red-orange ring. It spends the day on the darkside of my tank away from the halide.

Thanks again,

Chris

 

[rshimek]

Hi Chris,

Well, it sounds like you have a Diadema, but I can't tell about the species. Most "herbivorous" urchins will eat a little "meat" now and then, if yours is eating a lot of it, as it sounds like, I suspect it has had a serious dietary imbalance. What is the calcium concentration in your tank water? It may be eating these items to get calcium from them.

Most Diadema will eat fleshy or hair algae readily.

I don't think you have "defective" animals - the animal always does the best it can to stay alive given the conditions at hand. It sounds like there may be something peculiar going on within the tank.

:frog:

 

[ChrisM]

suspect it has had a serious dietary imbalance. What is the calcium concentration in your tank water? It may be eating these items to get calcium from them.

I've only had it for a few weeks. I have no idea how long the LFS had it before I got it. It was in a tank with no rockwork or algae, so it may have been starved. My tank conditions are:

75gal probably 90gal with sump

NO3 <5ppm
PO4 detectable with a LaMotte low range kit, but not quantifiable
Alk 10 dKH
Ca2+ 450 ppm
pH 8.1 before lights on 8.4 at lights out
Salinity 35-36 ppt
temp 80F at lights on 83F at lights out

I have turf algae, cyanobacteria and several unknown macro algae (maybe Acanthophora sp.) growing. I mainly got the urchin to help control the macros and turfs.

I don't think you have "defective" animals - the animal always does the best it can to stay alive given the conditions at hand. It sounds like there may be something peculiar going on within the tank.

You've never met my cats. Actually I don't think my animals defective, except for the four legged ones. Despite my remarks, I'm really very concerned about the well being of all my animals, which is why I'm posting here. I realize animals just "are", and that any atypical behavior they are exhibiting, is only atypical relative to the behavior they exhibit in the wild. A little glass bucket of artifical ocean is a far cry from thier natural habitat.

If there is something wrong with the tank, I don't think it's anything I can test for easily. Maybe I'll try to feed the urchin some krill and silversides, to try to correct any nutritional imbalances. Maybe offering it meaty foods will, at least, keep it from making a snack out my fish and corals.

thanks for your help,

Chris

 

[rshimek]

Hi Chris,

I think trying to feed the urchin some krill and silversides is an excellent idea. If it can get whatever fleshy things it needs, it may start eating algae.

Good luck!

 

[ChrisM]

I tried feeding it a silverside last night. I skewered the fish on a piece of plastic tubing, and placed it near the urchin. It came to get the fish right away, and grabbed it with it's "tube feet". (Comparative animal physiology was a few years ago, and my knowleged of urchin anatomy is lacking, so I'm sure that's not the correct term for the appendages on the body.) When I checked in the morning all that was left was a mangled fish head, so it looks like it ate it. I'm going to continue feeding it as much as it will eat, and see what happens. I'll let you know how it goes.


Chris

 

[rshimek]

Hi Chris,

Tube feet are indeed what would do the grabbing.

Please do keep me posted on this. It is an interesting set of observations. [thanks]

 

[racrumrine]

Any updates? How did the Urchin turn out?

Thanks,

Roy