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Pineapple Sponges: reef aquarium guide

“Who lives in a pineapple under the sea?” Okay, yes, everyone knows the iconic line from SpongeBob. But do you know you CAN find such a thing? Pineapple sponges, I mean. However, they’re not as easy to spot as a certain pants-wearing character. And some hobbyists aren’t fans of these underwater pineapples. (You may not be a fan of the show, either, but the comparison worked too well) The sponges aren’t as bad as you might imagine, however. Well, provided conditions in your tank aren’t sliding in an unfavorable direction. (Isn’t that always the case?)

Table of Contents: Pineapple Sponges

Pineapple sponges don’t get as much press as their larger, more impressive relatives. Not until they make “pests” of themselves, anyway. The invertebrate species fly under the radar in most saltwater aquariums. It’s only when you happen to notice a miniature pineapple (yes, it looks like one) adhered to the glass that you start frantically Googling to learn about them. And that’s where these links come in handy. They’ll steer you away from your panic mode and into an education mode.

What are Pineapple Sponges?

Pineapple sponges belong to the Sycon and Scypha genera, and there are multiple possible species. The invertebrates are an adaptive group, showing up globally. They prefer temperate climates, but the tiny pineapples have appeared as far north as Greenland (that’s COLD water!). If conditions are right, though, they’ll set down anchors and build colonies. (This is why they appear in your favorite display aquarium)

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Unlike other sponges, though, pineapples don’t go too deep. You won’t see them further than 6 feet (1.8m) down. And they require a substantial water current. Waves bring the nutrients pineapple sponges need to survive. Since they’re sessile (they remain anchored in one place, never moving around), they need an outside force to help them with resources. And they don’t have tentacles to gather in those food particles. That’s why they need the waves and current – but they have a limit. They’re NOT sturdy. Stagnant waters with intense sunlight will destroy the delicate structures of the sponge (that will come in handy to know in a minute).

As you can probably guess, pineapple sponges look like the fruit they get their name from. (Though some people call them Q-tip sponges) The tubes are studded with fine projections that resemble the leaves of the pineapple plant. It gives them a hairy or fluffy look that’s easy to identify – if established enough. See, pineapples don’t grow very large. At their most impressive, they top out at 4 inches (10.2cm). And most hobbyists find them when they’re much smaller.

Don't confuse Blastomussa corals with pineapple sponges

Blastomussa spp. coral (Note the vibrant colors)

Color Matters (in Sponges)

The “leafy” projections are the only ornamentation pineapple sponges get. You won’t find much in the way of exciting colors. It’s another way they fly under the radar. The soft tubes are usually beige, grey, brown, yellow, or green. And that color? It reflects the algae or diatoms growing on the surface – not the sponge itself. That’s because the skeleton is composed of near-transparent silica.

So if you notice a vibrant tube taking up residence in your tank, you need to pay attention. Even if there’s a suggestion of “hair” around the edges. Pineapples AREN’T colorful. But other invertebrates that can spell trouble for your reef tank ARE. And those intruders hitchhike into the tank on live rocks or coral plugs if you’re not careful:

Both groups look similar. And while they’re growing, they can resemble a sponge. Except for the fact they possess sweeper tentacles with nematocysts. Those stinging cells pose a distinct problem for the corals in your aquarium. Sponges don’t have that kind of weapon.

There’s no such thing as a colorful pineapple sponge. If you’re seeing a new burst of vibrancy, you need to figure out what’s invaded your tank – and then decide how to deal with the problem.

While growing, Caulastrea corals may look similar to pineapple sponges

Caulastrea spp. (While this variety isn’t colorful, it lacks the “hairy” projections)

Sponge Reproduction

Pineapple sponges can turn into problems in certain tanks (we’ll touch on that in a moment) due to their reproductive capabilities. As with others in the Porifera Family, they can undergo sexual or asexual reproduction. And it’s the asexual side of things you need to worry about.

Sponges bud. A miniature replicant of the parent forms at the base. It then grows, establishing a colony. But the story doesn’t end there. Like sea anemones – specifically, some of the more obnoxious species out there – sponges have incredible powers of regeneration. ANY piece from a healthy pineapple sponge can grow into a complete tube as long as the environment’s favorable.

This means if you have a tank suitable for the growth of pineapples, it’s easy to end up with colonies. And colonies. And MORE colonies. That’s where the “pest” label often comes in. But, as you’ll see, it may not be warranted.

Recognizing Pineapple Sponges in Your Tank

You may or may not see the pineapple sponges in your tank. It depends on the age of your aquarium, where they decide to take up residence, and how hard you look (or a combination of the three).

pineapple sponges on glass

New tanks in the process of cycling are common places for pineapples to show up. Why? Because they have excess nutrients. Sponges LOVE silica. But they also need as much nutrition as possible. A new aquarium will have a virtual buffet for a sponge colony.

The other place they like to show up is in sumps – for the same reason. This is where you usually keep your filters. And it’s where those excess nutrients hang out. Any time you have organic matter collecting, you can see pineapple sponges.

But you also want to scout out darker spots. While pineapples get their color (or lack thereof) from algae and diatoms, they don’t need light to survive. All of those nutrients come to them from the movement of the water. They actually prefer shadowed areas within tanks. So hobbyists usually stumble on them clustering in dark nooks and crannies with moderate to high water flow.

Pineapple sponges tend to come in colonies. You’ll see a veritable Bikini Bottom. But it’s not out of the ordinary to see one on its own. It depends on the nutrient situation within your tank – not to mention the lighting in that area. Given their reproductive capabilities, though, you should hunt around for others once you see one.

Preventing Pineapple Sponges

Hobbyists often fret over pineapple sponges. They’re not the most attractive invertebrates you can find in your tank. And it’s not like you see them on any fish store product lists. So you probably want to know how to keep them from entering your tank.

But here’s the thing: pineapples aren’t necessarily a bad thing.

What do sponges do? They filter nutrients. Even in the ocean, they’re a natural filtration system. And that’s the same thing these species do in an aquarium environment. You see pineapples in new aquariums because they take advantage of the nutrient boost. They actively participate in the cycling process.

  • Filter
  • Drop the tank’s nutrients
  • Disappear

All without any action on your part. In the time it takes you to research what the pineapple sponges are and how to get rid of them, they’ll probably start vanishing on their own. (Okay, maybe not THAT fast, but it’s a quick turnover) You don’t need to fret or worry about keeping them away.

And as long as you’re not overfeeding your fish and other invertebrates, you won’t need to worry about an explosion in the pineapple sponge population. Limit the resources the invertebrate needs, and you’ll limit the “pest.” (You can’t say that about too many other problematic species!)

If you really hate the idea of these bland-looking invertebrates, though, watch your nutrient levels. And keep your water as clean as possible. A quality protein skimmer and the best filters will help with the process.

Angelfish, especially dwarf angels, can help elimination pineapple sponges

Removing Pineapple Sponges

Most cases of pineapple sponges don’t need intervention. The fuzzy invertebrates will appear, assist with some filtration housekeeping, and then bow out of the picture. If they show up in your sump, you won’t even notice their visit.

However, there are exceptions. If you have nutrient levels through the roof, you can end up with a population explosion. This results in enough sponges to clog equipment and even out-compete your corals and anemones for the available resources. You don’t want that.

When you’re helpful houseguests turn into lazy slobs, it’s time to show them the door.

But it’s not a simple process.

Water Quality

Before you attempt any other removal process, you need to get your water quality under control. The more organic matter you have in your tank, the more you’re encouraging the growth of pineapple sponges. They’re sessile invertebrates, too. So it’s not like they’re ranging around the tank in search of food. That implies a problem with your cleaning routine or equipment.

a few pineapple sponges

It’s time to check your maintenance. Eliminating the extra nutrients will halt the progress of the sponges. It’ll also improve the health of your fish and other invertebrates. So replace your filters, ensure you don’t have pineapples blocking intakes, and give your substrate a thorough vacuuming.

You can also make adjustments to your water source. Pineapple sponges require silica to build their tube structures. Switching to RO/DI water for your water changes can reduce the amount of silica you introduce into the tank. If you’re already using RO/DI water, you may need to buy a test kit and check those levels.

Physical Removal

Leaving pineapple sponges alone is easy for one reason: Physically removing them from a tank is HARD. You’re not only contending with that nasty regeneration capability, but you’re also fighting with one of the sturdiest anchors in the invertebrate kingdom. Combine the two, and you’re creating pure exasperation.

Sponges adhere to surfaces. That prevents the tubular structures from getting tossed into the current. They need to stay in a constant water flow to receive nutrients and get their wastes whisked away. But all of that water movement would throw them around if they didn’t have a solid anchor. So they have “sponge cement” to stay in place. And trying to break that bond – without leaving something behind – is tricky.

Get some tweezers and a razor blade if you want to make an attempt. Also, wear gloves to protect your fingers. (Not from the sponge. They’re soft. The gloves will protect you from – well, you)

  1. Use the tweezers to gently pull the pineapple sponge free from rocks, corals, or other rocky surfaces.
  2. Grab at the base and pull gently but firmly.
  3. You don’t want to leave anything behind to regrow.
  4. On glass, use the blade to scrape the sponge away.
  5. Slide the blade as close to the glass as possible to get beneath that anchor.

Using a blade on rock or coral usually won’t work. You won’t have as much room to maneuver, and you’ll leave pieces behind. Then more pineapples will regrow. (And you have to start the process over again)

And while using chemicals MIGHT dissolve that silicate skeleton, you’ll end up altering the environment of your tank. It isn’t healthy for your fish or other invertebrates. Considering you have other, safer alternatives, it’s not worth it.

Some nudibranchs happily devour pineapple sponges

Lighting

Believe it or not, one of the easiest ways to eliminate pineapple sponges is to adjust your lighting. These little filter feeders prefer the company of darkness. And they’re sensitive. If you GRADUALLY change the intensity of the light reaching the colony, they’ll break down.

Take things slowly, though. You don’t want to shock any of the life in the surrounding area. For instance, if you have corals at the bottom of your tank, rotifers in your sump, or a burrowing species with a den in that back corner, a sudden spotlight will wreak havoc. As much as you might dislike those pineapples, you don’t want to risk damaging or stressing your other species.

“Housekeeping”

Pineapple sponges belong to the food web. Even hiding out in the dark spots of an aquarium, they continue to participate. And if you’d rather go the “housekeeping” route to eliminating their presence, you have a few options.

Top of the list is the nudibranchs. With thousands of species in the group, you’re spoiled for choice. You have different colors, shapes, and sizes – one’s sure to appeal to you. Rhinophores (the “tentacles” on their heads) help these gastropods identify the foods – and the rest of the world – around them. And some nudibranchs LOVE sponges.

You can find a species that will chow down on your pineapple problem with some careful homework. Of course, none of them feed exclusively on this particular sponge group. So you’ll probably want to go for a more general diet.

Angelfish are another popular group that snack on sponges. Given the smaller size of pineapple sponges, though, you may want to stick to the dwarf angelfish. And while angelfish enjoy chewing on the invertebrates, it’s not a specialist diet. This makes them easier to manage for every level of hobbyist.

A few other groups will snack on pineapple sponges if they happen to encounter one:

It’s not a guarantee they’ll eat your sponges, though, and some are safer to keep in reef tanks than others. It’s one more argument for allowing those pineapples to use up the available resources and disappear on their own. But if you’re desperate, you have options.

For More Information

Hobbyists start panicking when they see pineapple sponges. The invertebrates are usually unknown. What is that little fuzzy invader? Do you need to get rid of it? How do you get rid of it? Okay, it came back – now what? The questions pile up. And the debates on forums and message boards see-saw back and forth. As you’ll see below, there’s not a definite consensus about these invertebrates. (Poor little sponges – just trying to help you filter your aquarium)

This YouTube video discusses pineapple sponges (both sides of the equation):

 

Maybe pineapples are annoying, and maybe they’re not. Who can say? So let’s look at some examples of GENUINE aquarium pests for comparison:

Conclusion

Pineapple sponges get a bad rep. But is it warranted? Or do people see a strange, fuzzy invader and immediately break out the torches and pitchforks? It could be an overreaction. And, honestly, who’s to blame if the colonies get out of control? (That’s the only time these sponges present a problem)

Recognizing what the pineapples look like, in the first place, can help hobbyists from panicking. And then it’s a matter of understanding the function they provide to a tank. They’re filter feeders. Once they eliminate extra nutrients, they’ll break down and disappear. Problem solved.

But if your aquarium experiences overfeeding or struggles with cleanliness issues, you could find your equipment blocked by colonies and colonies of pineapple sponges. And while you want to blame the pest, it’s not precisely their fault.

Having read through everything in this article, what do you think? Should pineapple sponges get to stay, or do they go at the first fuzzy appearance?

References

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