Tuxedo urchin recently seeming off

[SayrinaDVM]

(Please forgive my tendency to anthropomorphize.)

Three months ago, we got two blue (*) tuxedo urchins from our LFS. [There was something interesting with their coloring, but it's probably unrelated to the current issue, so I've relegated it to a pseudo-footnote at the bottom of this post.]

We have a mature 32 gal BioCube with peaceful inhabitants and plenty of algae. We floated them to get them up to temp and then drip-acclimated, and both urchins settled in uneventfully. During the next 2.5ish months, they both seemed healthy and active; even during the day, we could typically find them mowing paths through the algae on some rock or on the back wall of the tank, always adorned with some assortment of algae wigs and shell/gravel hats.

I find their covering behavior hilarious and endearing, so when the slightly smaller urchin essentially stopped camouflaging himself about a week ago, I began to track him more closely, and I realized that he was also much less active. (I’m a night owl, so I can attest that he wasn’t gallivanting around the tank at night and just returning to the same spot in the morning.) A few days ago, I got worried when I found him nearly motionless, with his tube feet more or less tucked out of sight. I remembered reading that urchins typically enjoy eating nori, so I got a box of Omega One green seaweed and put some on a clip near him. After an hour or so with no reaction from him (not even the extension of a tube foot), it occurred to me that he might be unable to sense the nori and/or move himself towards it, so I relocated the nori to the tank floor in order to place him (and thus his mouth) directly on top of it. He had been sitting on a roughly horizontal bit of rock, and I was relieved—and a bit contrite—when I felt some brief resistance upon picking him up (which I took to mean that he had chosen to be on that rock?). I then discovered that he could move just fine, because within minutes of being placed on the nori, he scooted himself off it, onto the gravel bed, and eventually up the glass wall. He then spent the rest of the day moving along the front and side walls of the tank, so I watched his mouth/teeth with a magnifying glass (the Flipper DeepSee Nano) for any indication that he might be eating. I didn't see any, but our snails and mag scraper also keep the glass pretty clean, so I’m not sure how meaningful that observation actually is.

At some point that night, he moved off the glass and onto a different section of rock, and he has remained within a 3ish-inch radius of the same spot ever since (i.e., for the past two days). His spines are so short that I'm not sure I'd be able to tell if they became more droopy or less dense. Whenever I look at him, at least some of his tube feet are out, so that might be an improvement? The thing that puzzles me the most, though, is that I think the color of his interambulacral bands seems faded: instead of dark blue, it looks more like gray or gray-brown (depending on the tank lighting). The color difference doesn't seem as distinct in photos for some reason, but I gave it a shot:

Here is a picture of both urchins shortly after we added them to our tank three months ago:

The next two pictures are from yesterday evening. The urchin in the left picture is still behaving normally, and his interambulacral bands look about the same as when we first got him. The sad urchin is pictured on the right.

Potentially relevant photo details: The picture from three months ago was taken through the DeepSee Viewer by my husband with his Android, and both urchins were on top of the rock structure in the tank (and thus closer to the lights). Both pictures from yesterday were taken with my iPhone, and the healthy urchin was on a rock at the bottom of the tank, nearly touching the tank glass, so my camera was fully zoomed out, while the sad urchin was in a more shaded spot in the middle of the tank, and I did zoom in.

General Tank Info:
32 gal BioCube established about 5 years ago

Current [non-hitchhiker] inhabitants:

• Fish: green chromis, scissortail dartfish, zebra barred dartfish, citron clown goby, young-ish blue chromis, young green mandarin dragonet (obtained from Biota three months ago)
• Crustaceans: electric blue hermit crab, gold coral banded shrimp
• Snails: nerites (lots), ceriths (some), banded trochus (some), nassarius (we started with two, but we only see one of them regularly), and a large snail that was sold to us by a different LFS as a Nassarius ? (It does seem to behave like one, but measures 3+ inches in length...? That's a topic for a different post, though.)
• Corals: a frag plug's worth of emotional support zoas that one of the tuxedo urchins brought with him

Water parameters:
Temperature 77.5 F
Salinity 1.026

[Note: The rest are estimated from API's 5-in-1 test strips, but our Hanna ULR Phosphate and HR Nitrate kits are due to arrive in two days, so I'll have more accurate values then.]

KH 80 ppm (calculated dKH 4.47)
pH 8.0
Nitrite 0 - 0.5 ppm
Nitrate 40 ppm


From the bit of reading that I've done, it seems like starvation and high nitrates are frequently implicated in urchin mortalities. I know our nitrates are high, but for whatever it's worth, they've been around 20-40 ppm for quite some time now (definitely before we got the urchins), and the other tuxedo urchin's behavior hasn't changed. As for nutrient intake, the sad urchin has pretty much stayed on rocky areas with splotches of coralline algae on them, so I hope he's eating that, but I can't really tell.

Any and all thoughts/suggestions welcome. Many thanks in advance!

---

(*) At the store, both urchins’ interambulacral bands looked turquoise rather than the typical dark blue. Has anyone ever heard of anything like this? We’ve never seen them look turquoise again, so I assumed it was related to the lighting in the store, but the whole thing is just puzzling, because we had already said that we were going to get them (so it’s not like we needed to be persuaded that these urchins were extra special), and they weren’t being priced any differently.

 

[JumboShrimp]

Might it have become just a bit too famished (eating through all the food sources)!l before you caught the problem, and started adding the Nori? Might some large sinking algae-wafers help?

 

[SayrinaDVM]

Might it have become just a bit too famished (eating through all the food sources)!l before you caught the problem, and started adding the Nori? Might some large sinking algae-wafers help?

I can certainly try some large sinking algae wafers, though he’s currently chosen a particularly difficult spot to introduce food to in the rocks. I’ll also post some pictures of the tank for context. Most of the rock structures in the tank are covered in algae, so I’m not quite sure what to make of the fact that he seems to be choosing to attach himself to relatively bare patches of rock.

Front view:

Side view:

The best picture I can get to show where he’s wedged himself:

 

[JumboShrimp]

Now THAT'S an algae problem! I added a Tuxedo, a very large Mexican snail, and this Sea Hare (grew into a monster), and after just a week I had to start feeling the tank Nori and algae wafers! Get a Sea Hare. Lol!

 

[W31Olds]

I'm not an expert on Urchins but I do have 2 in my Tank. I would be looking at Testing your water. Your dKH of 4.7 is really low and with all that algae you may have a nutrient problem. Inverts need Calcium among other things to build and maintain their shells. I would start with a significant Water Change and see if that helps

 

[SayrinaDVM]

Friday night readings from Hanna tests:

Nitrates 33.8
Phosphates 0.26

As far as I can tell, the sad urchin is about the same; he’s still moving around the tank and I don’t think he’s dropping his spines, so the primary sign that something is off is that he isn’t engaging in any covering behavior (which he always used to do). I can’t tell whether or not he is eating, but I’ve also realized that I can’t tell with the healthy urchin either—I just assumed that the healthy one is still eating because none of his other behaviors have changed.

I’d like to try something other than the Omega One nori sheets, just in case there’s something particularly unpalatable about them. (After the sad urchin rejected both the green and the red seaweed, we presented our healthy urchin and tiger conch with new pieces of both kinds, and I don’t think they ate any either...)

So I have a few follow-up questions. Using cats as an example, when a cat’s appetite is off (and we’ve ruled out medical causes, which is where this analogy falls apart, but humor me), we first check about some things:
- Is the food bowl located somewhere less-than-ideal? (e.g., in a loud/high-traffic part of the house, next to The Scary Noise Machine (like a dryer or furnace/water heater), near their litter box)
- Is the food bowl too small and/or deep? (Some cats are more sensitive to whisker fatigue/overstimulation than others.)

Then if that doesn’t help, there are two “tricks”:
- Dialing the aroma up to 11: Find a wet food (the stinkier the better, so fish flavors tend to work well), add a bit of water, warm it in the microwave, stir well, then serve.
- Tricking them into a little taste: This works best with a sticky paste or gel, but could also work with wet food. Dab a bit on the cat’s nose or on top of either front paw. They’ll probably try to dislodge the offending material first (by shaking it off or wiping it onto their surroundings), but if that doesn’t work, they’ll eventually feel compelled to groom themselves. As this requires them to lick their nose/paw, they’ll get a little taste, which can sometimes be enough to stimulate their appetite.

(And if that doesn’t work, we move on to medical interventions, like appetite stimulants, and so the analogy falls apart again.)

Is there an urchin equivalent to any of the above?

- Are there any supplemental food types or specific brands of nori, algae wafers, pellets/flakes, etc. that your urchins seem to really like?

- What about fresh or frozen “human” veggies/fruits (that presumably aren’t nutritionally balanced but can probably be given occasionally as treats)?

- Are there any factors or tricks that could make food more enticing? For example, do you put the food clip in a specific part of the tank, fold/clip the nori sheet a certain way, soak the food in something before putting it in the tank, etc.?


Lastly, is there any kind of intervention that might help?

If I could find anything that he would definitely eat, I could theoretically turn an acclimation box into a temporary “hospital” (so it would be easier to feed and monitor him), but would that just stress him out more?

Thanks!

 

[SayrinaDVM]

I'm not an expert on Urchins but I do have 2 in my Tank. I would be looking at Testing your water. Your dKH of 4.7 is really low and with all that algae you may have a nutrient problem. Inverts need Calcium among other things to build and maintain their shells. I would start with a significant Water Change and see if that helps

Thanks! Would you recommend digital testing for magnesium and alkalinity as well as calcium? And are there any other ways you’d recommend evaluating nutrient quantity/quality?