I am writing this little guide on keeping marine sponges in aquariums in response to requests for more information on these unusual and intriguing aquarium inhabitants. While most of the information is the result of my own experience keeping and raising sponges, I also consulted several books and websites, included (but certainly not limited to) Marine Invertebrates by Dr. R. L. Shimek, 2003 World Book Encyclopedia, and Wikipedia. The following guide contains information on anatomy, biodiversity, care, and other information I deemed important enough to write about. Tempting to skip over, isn’t it? Most reef enthusiasts read these articles for the quick answers- What do I feed my tang? Does the sponge need light? Alas, sponges aren’t simple and the finer points of keeping Poriferans aren’t nearly as well known as they should be. Reading the following paragraphs about sponge anatomy and biodiversity will give you a much better understanding of your new inhabitant and keep you from getting confused by words like ‘spicule’ that are used later on in the guide. I hope this little guide helps future and accidental sponge owners provide optimal care for their sponges, avoid pesky species, and maybe even learn something new!
The Anatomy of Sea Sponges
All sea sponges have certain common characteristics. To differentiate species, scientists examine the sponges’ spicules- the ‘skeleton’ of a sponge. Although some sponges have exact shapes, most have ambiguous shapes that make identifying individual species basically impossible without a microscope. I will tell you how to harvest samples of sponges’ tissue for identification later. Spicules range in size, from about .01-.6 mm long. They are secreted by the sponge as the sponge grows. Sponges have no heads, no internal organs, and no limbs. All sponges have two types of openings. The first are small pores, commonly known as ostia. Ostia allow water to enter the body. The second type of opening sponges have are known as osculum, which allow water to leave the organism. Some advanced sponges have canals to transport water, as well. Canals and other openings in the sponge lead to many smaller chambers in the sponge. The chambers are lined with choanocytes (also known as collar cells), which trap food particles. Collar cells also have flagellum, which whip around, creating currents that move water through the sponge. Sponges have several other types of cells, including those which flow freely throughout the organism to aid in growth, regeneration, and reproduction. As described, sponges are covered in tiny pores which take in water. When exposed to air, the atria (channels and pores) in the sponge trap air bubbles inside the organism. In the wild, sponges are never exposed to air and therefore have not evolved a mechanism to force air out. For this reason, sponges exposed to air usually experience a fair degree of necrosis.
Sponges as Diverse Forms of Life
Now, let’s briefly examine the taxonomy of sponges. Sponges were among the first animals to appear on Earth over 500 million years ago, evolving into over 5,000 different species, whose range includes some fresh and almost all marine environments, from tropical reefs, to Antarctic seas. Originally classified as plants, sponges are now recognized in the kingdom Animalia, phylum Porifera. Zoologists have divided sponges into 4 different classes based mostly on structure. Sponges in the class Calcerea have limestone skeletons and are found in many diverse environments. Sponges belonging to the class Hexactinellida are mostly deeper-water marine skeletons with a silica-based skeleton, and are therefore rarely imported for aquarium use. This class of sponges may also be known as glass sponges. The next class, Sclerospongiae, is comprised of sponges mostly found in underwater caves with a silica-spongin based skeleton and a thick foundation of limestone. Due to their unique structure and environment, harvesting and caring for these sponges is extremely difficult and as a result, these sponges are justifiably rarely available to aquarists. Finally, there is the class Demospongiae, the most widely recognized class of sponges. This class includes freshwater and well known marine sponges. Members of this class may have skeletons made of spongin or silica, or both. However, for time’s sake, I will concentrate mostly on sponges in the class Calcerea and Demospongiae.
Sponges belonging to the class Calcerea are better known as encrusting sponges; sponges that often “hitch hike” on live rock (although we’re the ones taking the rock, hrm, hrm, hrm...) These sponges come in many forms; colors range from white, to deep maroons, to yellows, oranges, pinks, and green/blues. Some superbly interesting sponges native to Florida and the Gulf region are known as bubble ball sponges, or chicken liver sponges. They “droop” over pieces of rock; the body seems to be comprised of tiny white and light brown spheres covered in a clear sheath. Calcareous sponges are generally smaller than demosponges; the most common calcareous sponge is the tubular calcareous sponge (syconoids). Seldom over 1 inch in captivity, this sponge can thrive in tanks of all sizes as long as a suspended food is available. Another good candidate for aquarium keeping is Clathria species. This encrusting sponge is found in the range of the Caribbean to the Pacific, displaying colors ranging from pastels to white. Although individual specimens may not reach over one inch length, there are plenty of recorded exampled where they have spread quite a bit! As previously mentioned, identifying exact species of sponges is nearly impossible without examining the microscopic skeletal structure of the specimen. As a general blanket statement to cover the majority of calcareous sponges found on live rock, these sponges require moderate, but indirect flow and a steady supply of suspended food particles. It is best to keep them out of full light, as it may cause them to become overwhelmed with algal or bacterial overgrowth. Sponge larvae may be on your live rock when you get it, so be sure to keep all your rock completely submerged to ensure later sponge growth. Never, ever touch sponges with your hands, and never, ever expose a sponge to air.
Keeping demosponges is a little like playing with fire. Often available at local fish stores or via internet sites, demosponges may have beautiful, fingerlike structure, encrusting structure, or unique cup-like structures, to name a few. Demosponges are beautiful, colorful, fragile, and, to an aquarist not versed in Poriferan care, a possible time bomb. However, with luck and proper care, demosponges can create a breathtaking reef display. Most common demosponges available to marine invertebrate enthusiasts are listed below, along with a brief description of care and compatibility.
-Blue Finger Sponges (Haliclona spp.; native to Indo-Pacific)
One of the most beautiful and interesting sponges in the seas; this sponge’s fingerlike projections can reach heights of 12 inches. Haliclona prefer a swifter current, but will not tolerate water movement characteristic of most power heads. Like all sponges, it is reliant on filtering food particulate out from the water, but unlike many other sponges, it contain powerful toxins which allow it relative immunity from algal overgrowth. Because of the strength of these toxins, I would not recommend this type of sponge for aquarium care; this sponge will kill almost any specimen it grows on, and in the event of its death, it could quite possibly release enough toxins to kill other aquarium inhabitants (also known as “nuking” the tank). I’ll detail the keeping of toxic sponge specimens, later.
-Tree Sponges (Amphimedon spp., Ptilocaulis spp.; native to Caribbean/ Indo-Pacific)
Another beautiful specimen best left in the wild or in the care of professionals. Growing up to 18 inches, this sponge prefers dim lighting which replicates its natural environment, deeper tropical waters. Lighting may even damage some species! Another sponge super sensitive to flow; avoiding surge or wave-making generators in favor for a steady but diffused flow is the only way to prevent them from literally melting away. Due to the species’ seemingly nonexistent ability to prevent algal contamination, poor survival rates, and potent toxins, this type of sponge is poorly suited to captivity.
-Ball Sponges (Orange Ball Sponges, Cinachyra spp.; native to Caribbean/Indo-Pacific)
Although usually less toxic than Blue Fingers, some ball sponges may also be toxic; able to overgrow and paralyzing/killing immobile animals and plants. Gaps between openings may be covered in debris, forming a dirty looking layer between openings. These dirty spots are usually a sign the sponge is healthy and filtering the water for food. These sponges are not even bothered by minor algal overgrowth which usually accumulates on them!
-Orange Tree/Paddle Sponges (Clathria spp.; native to Caribbean or Indo-Pacific)
Such unique shape! In the wild, these sponges grow projecting laterally from vertical cliff faces, with paddle diameters approaching over 3 feet! As a result, in the aquarium, a fake cliff should be constructed and flow should be laminar along your fake cliff. Surges and other oscillating flows will harm this delicate Poriferan; so does bright light. However, unless the aquarist is willing to provide such specialized conditions, this sponge will usually die in captivity, releasing potent toxins into the water.
Sponges in Aquariums
Honestly, many of the most ornamental sponges are simply unsuitable to keep in small aquariums. The majority or demosponges fair best in AT LEAST a 50-100 gallon aquarium with well-established sand beds and microscopic fauna or flora. Demosponges must be securely attached to a rock in an area of acceptable flow and lighting. If precautions are taken, demosponge displays could certainly rival crinoids in exotic beauty. Calcareous sponges are generally ideal candidates for aquariums of all size; many even have colors or patterns as appealing as demosponges. For best results keeping sponges, a constant supply of suspended food is required. I personally use DT’s Supreme Reef Blend (Phytoplankton) every other day and DT’s Oyster Eggs on days where I do not use the phytoplankton. I have found my most successful sponge colonies exist in conditions of indirect to dull lighting and steady, medium current, but indirect flow. Another key to keeping happy sponges is to maintain clear water; small particles of sand or minerals can become lodged in the sponges’ tissues and cause rapid necrosis. If an area of a sponge is rapidly necroding, the take action as soon as possible. Test water, too- a sudden swing in a parameter may be the culprit. Like many corals, isolated necrosis can quickly devastate and entire organism. I personally recently began to use the additive Araga-Milk for my corals; I believe it also benefits the sponges.
Before Buying: Let’s Talk Care
Most sponges have one thing in common- they do not tolerate oscillating, pumping, undiffused, or wave-maker pattern flow. All sponges should be kept in areas with indirect but steady, ‘firm’ flow. Since sponges are filter feeders, in the wild they need a steady stream of water to get enough food. Flow should be strong enough where no particle will end up resting on the sponge’s surface, but gentle enough to not damage the sponge’s somewhat fragile spicules.
Few sponges will tolerate or thrive in bright lighting; most sponges that do like direct lighting prefer a red-end shifted lighting (A lower K rating such as 6500 K; 10000K is whiter light –higher ratio of blue wavelengths- and less beneficial). Sponges generally thrive in indirect or low lighting conditions; unless specifically told otherwise, put your sponge in a shadier part of the tank
When Buying Sponges
Buying a sponge specimen is sort of like buying Lottery scratch off tickets- you probably will end up losing at least once! Check your LFS to see if their live rock contains sponges; ask for special treatment when bagging the rock or volunteer to do it yourself- most LFSs ‘bag’ live rock by wrapping it in newspaper- an act which will decrease your chance of attaining a healthy specimen. If you are able to provide adequate care for an exact species, many LFSs will special order specimens. Ask to pick it up before they acclimate the specimen to their tanks. This will decrease the chance they’ll expose it to air. If your local LFS already has a specimen for sale, ask to put it on hold for a week or two. If the sponge does not decline in that time period (look for bleaching or melting of tissues) then the sponge was probably handled without much exposure to air. Please, do not harvest sponges from the wild unless you are familiar with the basic care of the specimen- a sponge found growing alone in an overhang in Florida probably won’t be well suited to a spot next to your Yumas.
Is it a Sponge or is it a Tunicate?
Tunicates are VERY different from sponges, but to the casual observer, they can appear quite similar. Below is a short list of features almost exclusive to either sponges or tunicates.
-Does not react quickly to poking, change in water flow, or changes in light
-Appears to have a spiny understructure
-Has several randomly placed openings, not arranged in geometric form (with exception of vase and finger sponges)
-Reacts quickly to stimuli
-Often has geometric shape
-Lives in colonies of several visually separate organisms
-Appears fleshy and lacks stiff support structures
Emergency Sponge Care
There comes a time in every pet owner’s life when Fido, Muffin, or Tweety has a cold or some manner of illness. Why should your friendly little sponge be an exception?
-If there is debris clogging ostia
This is a fairly common problem, especially after recently scrubbing algae off the glass or stirring up particulate. After the water settles, gently create a temporary current over the ostia by sucking and blowing on a section of airline tubing, dislodging the matter. Make sure you don’t bIf this does not work, use a sterile pair of tweezers, turn off all power heads and CAREFULLY manually dislodge the particulate.
-RTN (Random Tissue Necrosis)
There are a few different types of necrosis visible in sponges- the first is ‘bleaching.’ From my experience, I have not seen bleaching spread to more of the tissues once the underlying cause of the bleaching was taken care of. In fact, bleaching can even be reversible over time, provided proper conditions are present. More on this later.
Collecting Tissue Samples Safely and Humanely
To collect a tissue sample from your sponge, the most useful tools are a scalpel and a pair of forceps. Use the forceps to secure an area of the sponge, cut the area away cleanly with a sterile scalpel. To use the tissue in identifying sponge species, a book detailing spicule structure and occurrence, a microscope, and a slide making kit is needed. Slice thin sheets of the tissue with the scalpel to create slides; I’ve heard dying the tissue greatly enhances visibility. Check online suppliers for lab supplies and local universities for books on Poriferans. If you are trying to determine whether your sponge is a demosponge of calcareous sponge, you can use tissue samples to conduct at-home tests. Only about 4-5 mm of sponge tissue is needed to conduct this test. Simply use your forceps to handle the tissue (your hands’ oils will destroy the tissue!). Dissolve the sample in a little bleach. Add DI water, and rinse the remains. Glasslike particles should remain in the container. Add a little vinegar- if the solution effervesces (bubbles), then it is a calcareous sponge; if it does not it is likely a demosponge!
I hope this guide clears things up- please feel free to add information, or email me about sponges; I’m always interested.
Edited by jane of baden, 14 September 2006 - 06:19 PM.