That Fish Blog – Aquarium Advice and Information

Some of the most common questions we get from customers are about the relationship between clownfish and anemones (especially after the release of a certain animated movie several years ago). Aquarists see that relationship and want to replicate it in their own aquarium, only to find that the clownfish and anemone they brought home don’t seem to want anything to do with one another. “Why is that?!”, many ask. “I thought they couldn’t live without each other!” The truth is….they can. Anemones don’t need clownfish and clownfish don’t need the anemone, especially in aquariums where (hopefully) they don’t have any predators to hide from. In the wild, the anemone’s stinging tentacles give the clownfish somewhere to hide from and the clownfish’s messy diet gives the anemones some extra food (although there have been reports of clownfish actively feeding their anemones, but that’s another blog). Read More »

Hello, Frank Indiviglio here.  Please see Part 1 and Part 2 of this article for general information on Damselfishes and their close cousins, the Clownfishes, and for notes on the care of the beautifully-colored Percula clownfish, Amphiprion percula.

Damselfishes in the Aquarium

Damselfishes are generally small, brilliantly-colored and in near constant motion.  These characteristics, along with their general hardiness, render them quite popular with aquarists.

Despite their small size, most damselfishes survive quite well in aquariums with larger fishes.  However, most are very territorial and rather aggressive towards their own and similar species (please see below).

Taxonomy

Together with the ever-popular clownfishes, the damselfishes are classified in the Family Pomacentridae, which contains over 325 species.  Many are superficially similar in appearance but differ greatly in habitat choice, food preferences and other regards, and ichthyologists (fish scientists) describe new species regularly.

Marine Gardeners

Damselfishes seem inordinately protective of their territories, so much so that these tiny warriors will even attempt to drive off human divers!  Research has revealed that several species engage in “aquatic farming, with mated pairs protecting beds of algae, a favored food.  Thick mats of algae often grow within well guarded territories but are absent outside these territories, due to a large number of other fishes and invertebrates that feed upon algae. 

The industrious little damselfishes have even been seen to “weed” their algae beds by removing debris and, possibly, competing algae species.

Further Reading

An interesting article on the relationship between Cocoa Damselfishes, human activities, coral reef health and algae is posted here.

I’ll discuss the care of various damselfish species in future articles. Until then, please write in with your questions and comments. 

Thanks, until next time,

 Frank Indiviglio

Hello, Frank Indiviglio here.  Please see Part I of this article for information on the natural history of the clownfishes and their close relatives, the damselfishes.  Today we’ll take a look at the most popularly kept of the clownfishes, the beautifully-colored Percula clownfish, Amphiprion ocellaris.

Even before being skyrocketed to fame by the movie Finding Nemo, the Percula was an aquarium favorite, and one of the most widely-recognized marine fishes in the world.  Its brilliant orange and white coloration and seemingly “comic” mode of swimming endears it to all. 

Natural History

Hailing from the Indo-Pacific region (western Pacific and eastern Indian Oceans, including the Great Barrier Reef), this clownfish reaches a length of 3.2 inches in captivity; wild specimens are reported to exceed 4 inches in length, but captive bred animals are generally smaller.

Observations of free living Percula clowns indicate that they usually colonize magnificent sea anemones, Heteractis magnifica.  I have not read any research indicating that the various clownfishes seek out host anemones based upon their ability to survive within a particular species (please see Part I), but such would certainly be interesting to investigate.  Please note: Maldive Clownfishes are pictured here with a Magnificent Sea Anemone.

Clownfishes in the Aquarium

Like all clownfishes, the Percula is territorial and quite protective of the anemone in which it lives.  Generally only one mated pair can be maintained in an aquarium, unless it is very large and well stocked with coral and other sight barriers. 

Percula Clowns are omnivorous, and accept a wide variety of dry, frozen and live foods.   A mix of vegetable-based and meaty items should be provided.

Fortunately, captive bred specimens are readily available.  If considering a Percula Clownfish, please be sure to select a captive bred animal. 

The Anemone-Clownfish Relationship

Percula clowns do fine in captivity without an anemone in which to live, but not so
in the wild….there, clownfishes deprived of an anemone’s protection are quickly consumed by predators.  However, they are at their best when displayed with a living anemone, and when kept so will reveal a great many of their interesting interactions with these invertebrates (please see Part I of this article for further information).

The keeping of live sea anemones differs somewhat from fish-keeping.  For further information, please see the following articles on our blog: Unusual Invertebrates for marine Aquariums and Anemone Movement: Common Aquarium Questions .

Further Reading

Please check out the book I’ve written on marine and fresh water aquariums: The Everything Aquarium Book.

You can learn about clownfish natural history here.

Please write in with your questions and comments. 

Thanks, until next time,

Frank Indiviglio

Hello, Frank Indiviglio here. Damselfishes and Clownfishes are closely related, with all 325+ species being classified in the Family Pomacentridae. Among the most numerous and conspicuous fish on tropical coral reefs, a number make hardy marine aquarium inhabitants.

Range and Habitat

Damselfishes and Clownfishes are found throughout the world’s tropical and semitropical seas, with the greatest diversity occurring in the Indo-Pacific Region, especially off Australia; relatively few occur in the Atlantic and Eastern Pacific Oceans. They occupy a startling variety of habitats, with many species restricted to specific depths or specific areas of wave action. Several species can even enter brackish waters.

Identification in both the wild and pet trade is sometimes difficult, as their colors often vary from individual to individual; different populations of the same species may also exhibit unique color patterns.

Clownfishes and Sea Anemones

Clownfishes (aka anemonefishes) are well-known for their habit of living in close association with an invertebrate that is also an aquarium favorite, the sea anemone. Usually home to just one pair of clown fish, the host anemone forms the basis of their territory, and they rarely stray far from it.

Surviving Among Deadly Tentacles

Clownfishes were long thought to be immune to the anemone’s stinging tentacles, as they shelter right among them without being harmed (other small fishes would be killed if they attempted to do this). We now know, however, that the clownfish’s secret is not immunity at all, but an even more amazing adaptation.

Anemone tentacles fire their sting-bearing cells (nematocysts) upon contact with any organism that they come in contact with. The tentacles are coated with mucus which inhibits them from stinging one another. It seems that the clownfish secretes mucus which mimics that covering the tentacles of the anemone. Therefore, the anemone simply does not recognize the clownfish as prey, or even as a distinct organism!

In return for the protection offered by its host, the clownfish consumes parasites that might harm the anemone. By swimming about and fanning its fins, the clownfish may also increase the flow of oxygenated water through the anemone’s tentacles and about its base.

Do Anemones and Clownfishes “Need” One Another?

Aquarists often question whether clownfishes and anemones can survive without one other. It appears that the relationship might the best be described as “commensal”. By this we mean that each derives benefits from living in close association with the other, but they are not strictly limited to that situation.

The vast majority of anemones live without clownfishes. Clownfishes, however, seem somewhat more dependent upon the relationship. While they will live quite well “on their own” in the aquarium, experiments in the wild have shown that clownfishes without anemone hosts are quickly eaten by larger fishes.

Further Reading

The Florida Museum of Natural History has posted an interesting article and video on clownfishes here.

Next time we’ll take a closer look at the damselfishes and a favorite aquarium clownfish.

Please write in with your questions and comments.

Thanks, until next time,

Frank Indiviglio

Amphiprion sandaracinos image referenced from wikipedia and originally posted by Bricktop

I’d like to take time to welcome Frank Indiviglio to That Fish Blog. Frank is a former Bronx Zoo Zoologist, author and conservationist who’s worked with everything from fish to elephants. He’ll share his unique insights and work with various species on here, as well as the newly created That Reptile Blog & That Avian Blog. Welcome Frank!

Today I would like to pass along some interesting facts concerning fish you may be familiar with. I’ll focus mostly on aquarium trade species, with a few others added for good measure. I’ll add to the list in future articles. Enjoy, and please share your own store of unusual facts with us.

Finding a mate in the dark, featureless expanses of the deep sea poses quite a difficulty. Male benthic anglerfishes, such as Ceratias uranoscopus and related species, solve this dilemma by biting onto the first female they encounter. Thereafter, the male’s internal organs degenerate and he remains fused, by his mouth, to the female – surviving on nutrients circulating in her blood and periodically releasing sperm to fertilize her eggs!

Unique among the world’s fishes, male sticklebacks (small fishes of the family Gasterosteidae that inhabit marine, brackish and fresh waters), use kidney secretions to glue plant materials together when constructing their enclosed, bird-like nests. This behavior, along with their zealous protection of the eggs, helped spur the development of the aquarium hobby in Europe in the 1700s.

Cichlids found in Africa’s Lake Malawi are among the most enthusiastic of nest builders. Although measuring but 6 inches in length, males of one species create circular sand mounds that can exceed 3 feet in diameter, while another excavates 10 foot wide pits. Up to 50,000 such structures may be constructed in the same general area by a displaying group, or “lek” of males.

Marine damselfish, such as Stegastes nigricans, are unique in practicing a form of underwater “farming”. Pairs form territories around beds of marine algae (“seaweed”) and drive off fishes, shrimp, crabs and other creatures that show interest in this favored food.

Clownfish, such as the commonly kept percula clownfish, Amphiprion percula (or its cousin, the false percula, A. ocellaris, of “Nemo” fame) live unharmed among the tentacles of sea anemones — marine invertebrates that sting and consume other similarly-sized fishes. Anemone tentacles respond with a sting upon contact with any alien body, but are prevented from stinging themselves by chemicals in the mucous that they secrete. The clownfish, it seems, produces the same chemical in its own mucous and hence is not recognized as food.

Fishes lack external ears but do have inner ears that pick up the water pressure changes which accompany sounds. Aided by the Webarian Apparatus, an organ that connects the
inner ear to pressure-sensitive gas in the swim bladder, species such as carp and goldfish hear quite well and can communicate through vocalizations (perhaps it is not so odd to talk to your pet after all!).

Among the animals that are kept by people for their fighting abilities, none are as small as brackish-water fishes known as wrestling halfbeaks, Dermogenys pusilla. These thin, 3 inch-long warriors are the subject of staged matches in betting parlors throughout Thailand and Malaysia. Fights rarely result in injury, except to the wallets of losing bettors!

Despite popular belief, koi, Cyprinus carpio and goldfish, Carassius auratus, are not closely related. Goldfish, the first of any fish to be domesticated, were first kept by the Chinese over 2,000 years ago. Koi (the word means “carp” in the Japanese language) originated in the Black Sea area and arrived in Japan as a food source. They were first bred for domestic traits in Nigata, in northeastern Japan, in the 1820’s.

Ichthyologists discover new facts about fish on a near-daily basis. You can read articles about their findings at:
http://sciencedailey.com/

Thanks Frank,

Until Next Time,

Dave