Many sponges are colorful, easy to keep when healthy and correctly transplanted, readily available and inexpensive – so it’s a wonder more marine hobbyists don’t keep them. And while they may not do much in aquaria compared with active swimmers – sponges can certainly accentuate an aquarium reef with a much-needed splash of color.
There are more than 5,500 recognized species of sponges worldwide but just a handful are kept with success. Most are not suitable for aquaria: some come from deep-water locales, others can cause painful skin reactions in humans, still others will attack and eat or kill corals and some grow so slowly that it would be akin to harvesting a redwood tree (scientific estimates peg the upward ages of the largest Caribbean barrel sponges, Xestospongia muta, which are big enough for scuba divers to disappear into, at more than 2,000 years).
When you are able to transplant a healthy specimen, it’s like anchoring a “living lung” onto the live rock in your tank. The porous body structure, aka the aquiferous system, of sponges allows them to “inhale” huge volumes of tank water, while removing nearly microscopic bits of organic food particles as well as oxygen. The water is then “exhaled” along with carbon dioxide and other waste products. Another amazing property of these animals is their ability to regenerate themselves, much like the metallic cop in Terminator 2: Judgment Day, because of specialized regenerative cells.
Sponges can move prodigious amounts of water through their bodies every day and are often recognized as wonderful natural filters. According to one study, a 10-centimeter-long Leucandria sponge, with the diameter of a drinking straw, is able to process more than 5 gallons of water daily.
Sponges that are especially tough and adaptable to life in aquaria, perfect for beginner marine aquarists to try their hand at, are the lavender tube sponge (Callyspongia vaginalis), chicken liver sponge (Chondrilla nucula), red boring sponge (Cliona delitrix), orange ball sponge (Cinachyra kuekenthali) and orange fan sponge (Axinella bookhouti).
• Axinella bookhouti is an Indo-Pacific sponge that is reef-safe, orange in color and has a stalk with fan-shaped top. It makes a very pretty addition to someone’s reef aquarium.
• Callyspongia vaginalis looks like a cluster of gray, blue or purple smokestacks. These make very attractive additions, too.
• Chondrilla nucula is toxic to fish and should not be kept with reef fishes that have a penchant for grazing on sponges, such as many angelfishes, parrotfishes, trunkfishes and filefishes. This green to brown encrusting sponge is relative easy to keep; however, it isn’t especially attractive.
• Cinachyra kuekenthali is orange and ball-shaped, or it has a stalk with a knobbed protuberance on top.
• Cliona delitrix is a red encrusting sponge that usually kills any corals it overgrows. This species often has the appearance of being covered in white dots, which are a commensal species of zoanthid (Parazoanthus parasiticus).
“Airing” on the Side of Caution
One of the keys to being able to successfully keep these and other sponges is to make sure you initially acquire a healthy, properly harvested specimen. Since sponges possess the ability to reproduce asexually (i.e., fragging and budding) like corals, one of the best sources of a healthy sponge is from other hobbyists who have healthy sponges.
Of course, you’ll always want to quarantine any new specimen you bring home prior to introducing it into your own tank. The water conditions in the quarantine tank as well as the eventual tank the sponge will be introduced into should closely replicate the aquarist or local fish store tank you originally got it from.
One of the lead causes of sponge mortality is that they are exposed to air prior to the end of the supply chain – your tank. When removed from the water and exposed to the air, a sponge’s unique “water-moving” physiology sucks in air that cannot be removed once it becomes trapped internally in the sponge. The air kills the sponge from within. It is almost like drowning but in reverse.
And while you can’t be there when a specimen is taken from its home waters, you can certainly purchase sponges (as well as all other aquarium animals) only from reputable dealers who ensure that their animals receive the best treatment possible at every step of the supply chain.
Unhealthy sponges have a mushy feel as well as white or gray dead spots. Some sponges naturally have a mottled appearance; as a result, it is recommended that aquarists new to keeping sponges go with more uniformly colored species. In this way, first-time spongekeepers will be better able to pick up on the telltale clues as to a sponge’s overall health.
Sponges should be attached to a small piece of live rock. Likewise specimens must be retrieved, bagged and transplanted underwater in order for them to have a chance to do well. Although there are photosynthetic sponges, those mentioned in this blog are all small-particle filter feeders. These sponges also typically come from shallow, sun-bathed reefs with tidal exchanges and constant wave action. Similar conditions in the aquarium, good lighting and moderate water flow, will help these unique animals to thrive in captivity.
Many tropical reef sponges live from 20 to 100 years in the wild, and there’s no reason yours can’t live for several years in your setup as well.
“You know you’re a fishkeeper when you wonder how deep the ocean would be without sponges.”
— “Funny Fish One-Liners” (submit yours at FishChannel.com/OneLiners)