Urchins - how many is too many?

ThunderGoose · Oct 25, 2017

I hit the urchin jackpot with some live rock this year. I have found 3 long spine urchins and one that looks like the a "pincushion" or "pink" urchin (short spines, loves to carry things around, especially 2 of my feather duster worms that didn't bury into the substrate).

Add to that number my pre-existing tuxedo urchin and I now have FIVE urchins in my 55 gallon reef tank.

That seems like too many. Any ideas about stocking density? I'm particularly worried about the 3 longspine urchins since they can grow to be 10" each!

Thanks!

Paul B · Oct 25, 2017

I used to have an urchin collection business and one time I collected to many so I had to put 25 of them in my reef. All 25 decided to spawn at the same time turning my tank into Cool Whip. I had to quickly diatom filter the tank which cleared it up and I didn't lose anything. But I never did that again.

themcnertney · Oct 25, 2017

Probably too many in a 55. Even one in a tank that size is a bit of a risk.

nautical_nathaniel · Oct 25, 2017

I'd say rehome the longspines if you can, they need lots of space and will cause issues with their long, thin, easily broken spines sticking into everything. My black shortspine urchin poked one of my candy cane corals and severely damaged it so I would imagine that sort of situation would be more common with a longspine.

I've always heard they do well in large predator tanks as long as the fish aren't big triggerfish or anything else that isn't afraid to go after urchins.

themcnertney · Oct 25, 2017

Heres why I am not a big fan of longspine urchin (although I still have mine)...

Dan McNertney said:
One time this guy got me under the finger nail. Spine broke off and was a good 1/4" under the nail. I couldn't remove it. Arm went numb and was pretty painful. Called poison control and they told me to go the ER. When I arrived I checked in. Was immediately rushed to a room. They soaked my finger in iodine and warm water. Given I live in Akron Ohio and they hospital I went to has never had a documented case and didn't know how to treat it. They called some hospitals on the coast. Anyway they ended up numbing my finger with some local antiseptic. Used a scalpel and had to cut out the spine from under the nail. Stitched me up and sent me home.

Two weeks later my buddy was having a conversation with a lady friend of his that she had worked at the hospital that night. Guy came in and stung by a sea urchin. He was like I know him. That's my friend dan.

S-t-r-e-t-c-h · Oct 25, 2017

Dan McNertney said:
Heres why I am not a big fan of longspine urchin (although I still have mine)...

It always feels weird hitting "like" on posts like this, while I'm squirming in my seat...

75galOCD · Oct 27, 2017

I'm under the impression urchins survive on the nuisance algae and end up putting themselves out of a lunch, that being said I love my urchin he keeps his costume jewelry in motion, blows my mind. I think a tank would have to be algae rich to support one.

PurduePete93 · Oct 27, 2017

I'm on my 3rd trade back cycle this year with my LFS and black spiny urchins. Bought a small one, grew to 6-8 inches, brought him back to LFS and they swapped him out for a small one. Rinse & repeat. Love watching them grow. One of the coolest things in my 90g reef.

Grey Guy · Oct 27, 2017

75galOCD said:
I'm under the impression urchins survive on the nuisance algae and end up putting themselves out of a lunch, that being said I love my urchin he keeps his costume jewelry in motion, blows my mind. I think a tank would have to be algae rich to support one.

I fed mine cubes of veggie food. It would move in on it pretty fast. Got to be about a foot in diameter. Good deal if one can keep trading in for a small one. I know what you mean about the jewelry. Mine was circled with stunning blue diamonds. I thought that it looked like an alien space craft. My rock work is really solid right now. Maybe I’ll get another one.

LobsterOfJustice · Oct 27, 2017

That many urchins is okay, but the fact that they are longspines will be an issue. Imagine three basketballs roving about the tank. Although you might be lucky and they could just be a small rock-boring variety.

When I first got into the hobby, I had a longspine for a while in my 75g but it quickly outgrew the tank. Traded it to someone with a 180g and it quickly outgrew his tank too. Later on I kept 4 at a time in a 90g for a while... no issues, but none were longspines (had a rock-borer, tuxedo, pincushion, and pencil). You will have to feed them, they will eat nori.

Jacobscorals · Oct 27, 2017

In a reef one is one too many and something will happen

nautical_nathaniel · Oct 27, 2017

Jacobscorals said:
In a reef one is one too many and something will happen

My black shortspine is a model citizen 98.7% of the time. (See above for the 1.3% time it was bad)

They are super beneficial on a natural reef, take away the urchins and it won't be too long before the whole reef suffers.

pirate2876 · Oct 27, 2017

I have 2 in my 120 and that's too many sometimes. If you like to have frags moved around arbitrarily or, if you enjoy looking for missing frags behind rock work, include as many as you like.

Jacobscorals · Oct 27, 2017

Must be why they are killing them to save the kelp forests.they completely kill your live rock and eat coral and bulldoze everything in your tank and will eat healthy fish

LobsterOfJustice · Oct 27, 2017

Jacobscorals said:
Must be why they are killing them to save the kelp forests.they completely kill your live rock and eat coral and bulldoze everything in your tank and will eat healthy fish

Lol, what? This ranges from mostly true (bulldozers) to wrong (kill your live rock) to completely absurd (eating healthy fish).

I will admit they are bulldozers. Glue your frags, it’s a habit I got into a long time ago. Urchins aren’t the only things that will move frags around.

cracker · Oct 27, 2017

I have 2 small tuxedo's in my 75. I will be putting one in the 180 soon.They do a great job on algae.

SashimiTurtle · Oct 27, 2017

I HAD 2... pin cushion and tuxedo. I now have one. The tuxedo didn't make it, pin coushion has demolished a 10g tank full on macro algae and I need to order more. I'm between a 75g that sprung a leak and cycling a new 35g. I wouldnt put more than one per 100g unless you plan to suppliment them with algae to eat. They will starve each other out.

Best Fish-Jake · Nov 8, 2017

Everything said above is why I love the 2 short- spines urchins i have in my 30g. (I havn’t had problems with coral-stabbing like @nautical_nathaniel explained)
Very hardy critters, as long as you have green algae and/or some calciferous algaes they will do just fine. I have no visible algae in my tank (aside from bubble algae and coralline) and both short spine urchins have grown dramatically since their introduction.

ThunderGoose · Nov 9, 2017

I re-homed the three long spines and I've noticed fewer frags being knocked around. I kept the short spine and the tuxedo. The tuxedo is the least troublesome but the short spine is highly entertaining. She seems to have settled on carrying around two of my feather duster worms, some shells and a fragment of macroalgae. The feather duster worms don't seem to mind and are, to my surprise, doing just fine. I really enjoy these guys despite their tendency to redecorate the tank.

Thanks for all the input.

SirenBethany · Mar 15, 2024

LobsterOfJustice said:
That many urchins is okay, but the fact that they are longspines will be an issue. Imagine three basketballs roving about the tank. Although you might be lucky and they could just be a small rock-boring variety.

When I first got into the hobby, I had a longspine for a while in my 75g but it quickly outgrew the tank. Traded it to someone with a 180g and it quickly outgrew his tank too. Later on I kept 4 at a time in a 90g for a while... no issues, but none were longspines (had a rock-borer, tuxedo, pincushion, and pencil). You will have to feed them, they will eat nori.

If there isn't enough algae to graze just supplement. I feed my Urchins Nori, Wakame, chunks of clam I buy frozen at my local natural foods store. I also have fed scallop chunks and black cod before. I noticed when I put a piece of black cod in the sand a bit for my snails my sand Sifting Sea Star ate some too. I just bought a small Black Long Spine and fed him a little piece of thawed clam and it's eating right now while drip acclimating lol. Get those suction cups clips for feeding. You just clip the seaweed in and your urchins will come gobble it up.