The Power of an Urchin

There are a few types of urchins available to the home aquarium and it may be hard to know which one is for you, if any at all. We’ll discuss some tips for keeping an urchin, whether or not you should get one, and even what type may work best for your tank.

Why even get an urchin?

I felt this was the best question to start with. Most urchins available to us are ravenous algae eaters. They don’t tend to get picky with the type of algae although they do certainly have their favorite types just like fish. If your tank is nutrient rich and has an outbreak of algae you may consider one of these helpful algae bandits to rid you of your problem. They also love to eat coralline algae. If you tank starts to grow an abundant amount of coralline, they will help keep it in check.

What types are available

They do come in different sizes and price ranges. They also have different personalities and how they react being in a tank. We’ll discuss some of the more common types that are readily available in the hobby and are reef safe, meaning they can live with corals just fine.

Black Long Spine – These urchins have long spines as you probably guessed in the name. Longest in the hobby trade at least. While the main body can get as big as a baseball, with the spines it reaches the size of a basketball! Naturally these are only for the large aquariums in the hobby because of their sheer size. They do really well in predator tanks too as they tend to get left alone. A benefit of these urchins is that they don’t feel the need to cover themselves with parts of your tank like others do. I guess they feel really safe behind those massive spears on their head and, honestly, I can’t blame them.

Black urchin from Tampa Bay Liverock

Tuxedo – These urchins are perhaps one of the most popular types available. They come in a couple different colors, mainly red and blue, and they stay small reaching on average three whole inches. That’s it. These guys do well in even nano systems because of their small size but don’t let the size confuse you with their appetite! They will still ravage through the algae patches like nothing else will. They do have one little quirk and that is that they disguise themselves with stuff around them. In nature it’s a clever trick to fool passing predators. At home however, it can be annoying when they decide to take your newest frag plug for a little walk then leave it behind the rocks so you can’t reach it again. If you decide to house one in a reef tank just make sure you glue everything down that you don’t want to see scooped up!

Blue tuxedo urchin

Pincushion – One of the cheaper options, you can usually find them around $10 the size of a half dollar or even smaller. What the stores don’t tend to tell you is that they get wide – very wide. Around 10″ in fact. Not nearly as tall as the black long spine however, these should still be housed in larger tanks to allow them ample room to roam and eat their spiny hearts out. They also tend to hide themselves with materials found nearby as their spines, like the tuxedo urchins, are rather short. Most tend to be a pretty pink color which can add a splash of color to any tank.

Tiny pincushion urchin

Long term feeding

So you had an outbreak of algae and got an urchin of some type. You were shocked when all that algae that overtook your tank was gone in a matter of days! “Now what?” you ask yourself. The answer is simple – just keep feeding algae! We can buy sheets of algae at stores like Petco or perhaps even your local grocery store. Check if they have an Asian food aisle and you might find dried seaweed there. Make sure it has no additives; the only ingredient should be seaweed or nori. Some recommend holding a sheet of algae near the urchin until it grabs on but this is time consuming. Their not race horses after all! I found an easier solution for my pet urchins.

When the lights go off, or right before, I take a small piece of rubble rock, a rubberband, and a small sheet of algae. I wrap the rock in algae and rubberband it to keep it attached. Simply drop the rock in an easy to reach part of the tank and it’ll be clean in the morning.

The downsides

Some people may worry about the spines poking you. In reality, the only urchin who will try to poke you is the long spine if you are not careful. Tuxedo and pincushion urchins are harmless and you’re more likely to break their spines off than they are to poke you. No matter what, it’s important to find your urchin before you go sticking your hand in places you can’t see anyways. The other concern I hear involves their spines being poisonous. As far as I can tell, their sting is no more potent than a bee sting. I’ve been poked by a long spine urchin and, while it did hurt, it did not cause serious injury like some might think.

The only other downside I can think of involves coralline algae. Some people really love to have coralline coat everything in their tank, turning rocks into nice shades of purples or reds. Urchins will always target this algae and, depending on the tank size, may even eat all of it up. If you don’t care for this calcium based algae to cover your equipment, then having an urchin is actually a plus here!

I hope this helps you decide if you want an urchin or not. They are one of my favorite critters in my reef tank and I couldn’t imagine a tank without one. Comment below with your favorite type or why you would/wouldn’t keep one!


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