That Fish Blog – Aquarium Advice and Information

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

Hello, Frank Indiviglio here.  This Southeast Asian fish’s slender, 3-inch- long body belies its reputation as a fearsome combatant.  However, in betting parlors from Thailand to the Sunda Islands, matches between male wrestling halfbeaks (Dermogenys pusilla/pusillus) rival those featuring the better-known bettas (Betta splendens) in popularity.  In contrast to bettas, battling halfbeaks rarely inflict any serious damage…other than to the billfolds of losing gamblers!

Description and Habitat

Halfbeaks sport a startling adaptation to surface feeding…their immobile lower jaw is more than twice the length of the upper.  This, along with their subtle beauty – a silvery body highlighted by hints of blue and green – renders them a most unique addition to one’s collection. 

Halfbeaks inhabit estuaries and other areas of fluctuating salinity, and, while sometimes kept in fresh water, are at their best in brackish water aquariums. 

Feeding Wrestling Halfbeaks

Halfbeaks are highly specialized surface feeders and rarely if ever swim to lower depths in the aquarium. They tend to be picky feeders and prefer tiny live invertebrates such as mosquito larva, brine shrimps, fruit flies and Daphnia. Chopped blackworms may be taken, but these sink quickly and so must usually be offered via forceps (tedious but effective!). 

Halfbeaks may be habituated to flake and frozen foods, but the progeny of such fishes rarely reproduce, most likely due to a nutritional deficiency.

The Halfbeak Aquarium

While visiting pet stores and aquariums in Japan, where halfbeaks are more commonly kept than in the USA, I was surprised to find that multiple males were often housed together.  I learned that males will co-exist in large, well planted aquariums if emergent and surface-dwelling plants are grown as sight barriers.  Watching the threat displays and interactions in such aquariums was most interesting, and cast these little fellows in a new light for me.

A unique habitat preference and feeding style dictates that halfbeaks be kept in long, shallow aquariums and, with few exceptions, in single-species groups.

Breeding Halfbeaks

Wrestling Halfbeaks are live bearers, with healthy females giving birth every 30 days or so; males may be distinguished by a bright red blotch located in front of the dorsal fin. 

Unfortunately, adults are quite cannibalistic, and the fry rarely survive.  Breeding traps are not recommended, as the birthing process takes several days and females become stressed by long confinement in small areas.  Thickly-planted aquariums, with much of the vegetation at the surface, offer the best chance of success. 

Further Reading

Detailed information on the natural history of these and related fishes is posted at ZipCodeZoo.com.

A book I’ve written, The Everything Aquarium Book, addresses the care of brackish water fishes in detail.

Please write in with your questions and comments. 

Thanks, until next time,

Frank Indiviglio

Halfbeaks image referenced from wikipedia and originally posted by Neale Monks
 

Hello, Frank Indiviglio here. Sticklebacks hold a special place in fish-keeping history – their fascinating breeding habits are credited with inspiring the development of the aquarium hobby in Europe in the 1700s.  The Sea Stickleback (Spinachia spinachia) is one of the group’s few marine representatives, and a good candidate for one of the most fascinating fish breeding experiences imaginable.

The Sea Stickleback is native to the cool waters of the Northeastern Atlantic Ocean, along the coast of Northwestern Europe.  One of the larger sticklebacks, it attains a length of 8 inches or so and is quite hardy in the aquarium. It stays along the coast, rarely straying into depths exceeding 15 feet.

Underwater “Bird Nests”

Male sticklebacks construct tiny nests consisting of plant material held together by secretions from the kidneys.  Clad in vibrant breeding colors (sea sticklebacks sport bronze and silvery bars and silver-yellow abdomens) they then display for the females, who lay their eggs within the nests.  Females have been shown to preferentially choose water flowing from nests of unmated males, even when kept out of sight of the nests.

The brooding male guards the nest from any and all intruders, exhibiting aggressiveness that is far out of proportion to their size.  I once observed a male three spine stickleback (Gasterosteus aculeatus) chase off a cunner that outweighed him a hundred fold.

Diet

In common with their relatives the seahorses, sticklebacks prefer live foods such as brine shrimp, blackworms, Mysids and Daphnia.  I’ve had some individuals take frozen foods, but such is by no means a certainty for all. I’ve found that sticklebacks seem to require quite comparatively large amounts of food, and lose condition rapidly if not fed adequately. 

Sticklebacks are fairly slow feeders, and will be out-competed by active species.  They are also quite pugnacious and prone to “fin nipping” their less agile neighbors.  Marine species get along well with spider and hermit crabs, small puffers and sea stars. 

Spawning Sticklebacks in the Aquarium

We are indeed fortunate that such unusual fishes are rather easy to breed…watching them do so is a treat rarely afforded those who study marine fish.  Although quite territorial, small groups will co-exist if enough nest sites are available.  Be sure to provide widely spaced groups of sticks and plants so that nesting pairs may have the privacy they require. 

Several species will come into breeding condition if their water temperatures are allowed to fluctuate with the seasons, i.e. by keeping them in an unheated tank in a room that experiences seasonal temperature variations.  You should also seek to provide a light cycle tuned to that they experience in nature.  

Native Sticklebacks

Unfortunately, like many temperate species, Sticklebacks get very little attention from aquarists these days. 

The Sea Stickleback is not readily available in the USA, but a number of other species can be collected here and kept in a similar manner.  I have had good luck in breeding the Three-spine Stickleback (Gasterosteus aculeatus) in a densely planted marine aquarium.  This species is usually described as a brackish water fish, but those I collected from the Great South Bay on Long Island, NY thrived under typical marine aquarium conditions.

Further Reading

An informative account of stickleback collecting and breeding is posted at www.glaucus.org.uk.

Please write in with your questions and comments. 

Thanks, until next time,

Frank Indiviglio.

Ninespine Stickleback image referenced from wikipedia and originally posted by Dryke.
Sea stickleback image referenced from wikipedia and originally posted by Visviva.
 

Hello, Frank Indiviglio here. Among the 150+ species of catfish classified in the genus Corydoras, all native to Central and South America, we find some of the most beloved of all aquarium fishes. Yet despite their willingness to breed in captivity, not many aquarists make the effort. As we will see, however, the droll cory cats employ one of the fish world’s most unusual breeding strategies…they are definitely worth a closer look!

Startling Reproductive Behavior

Female cory cats are larger than males, and their body has a thicker, more rounded appearance. In some species, the male’s dorsal fin is thinner and higher than the female’s and is held in a noticeably more erect position.

Corys may breed in either pair or group situations. Males chase gravid females, with the pair eventually lying motionless and perpendicular to one another (this is known to aquarists as the ‘T-Position”). The male lies on his side, and, amazingly, the female then uses her mouth to withdraw sperm from his vent.

Fertilization – Internal or External?

How fertilization actually occurs is still open to some discussion. Most ichthyologists believe that the sperm exits the female’s gills, and is shunted to a unique cup that she forms with her pelvic fins.

Upon obtaining the sperm, the female lays 1-5 eggs into this cup. She then moves off to a pre-cleaned site, usually a plant or the aquarium glass, where she glues each egg individually. She repeats this process with the same or another male until her clutch of 10-25 eggs is laid, an ordeal that may last 3-6 hours.

Some researchers have suggested that the sperm passes through the female’s digestive tract, to be released along with the eggs, or that the female expels the retained sperm upon the eggs. In any event, a most extraordinary means of fertilization…why such a strategy would evolve has not, to my knowledge, been explained.

Breeding Corydoras

While Corydoras cats may spawn spontaneously, the most consistent results will be obtained if cool, highly oxygenated water is added to the aquarium, simulating the drop in temperature and rise in water levels that accompanies the start of the rainy season in most Corydoras habitat. Dropping the aquarium’s water level beforehand may also help.

While various species differ in their requirements, the formula that I have used for bronze corys (C. aeneus) seems to work well in general. After dropping the water level for 2-3 weeks and maintaining it at 76 F, I add water of 60 F in an amount equal to 1/3 the volume of the tank.

Caring for Eggs and Fry

The eggs can be left in place and the adults removed (some are egg predators), or they can be carefully transferred to a rearing aquarium (they are fairly large and sticky for a day or so after deposition).

The fry should be housed in shallow water (3-4 inches) at first, as constantly rising to the surface for air will weaken them significantly.

Cory cats are, despite their “scavenger” reputation, highly specialized predators on tiny invertebrates. Their fry are best reared on live blackworms, brine shrimp and Daphnia, with animal-based flakes and pellets being added as they grow.

Plan to be in it for the long haul…a bronze cory in my collection is nearing 21 years of age!

Further Reading

Peru’s popular panda cory (Corydoras panda), described in 1969, favors cool, fast moving streams. To read more, please see

http://www.redorbit.com/education/reference_library/fish/panda_corydoras/2190/index.html.

Please write in with your questions and comments. Thanks, until next time, Frank Indiviglio.

Greetings! The big news this week? MACNA!! Our team is on location in Atlantic City for this year’s main event, and Dave will be tweeting on all the cool stuff going on there. I’m sure we can also look forward to a blog recap highlighting the showstoppers.

In the news this week: more new species. I’ve said it before and I’ll say it again, the diversity we find on this little blue planet blows my mind. This time the newly discovered critters were found at around 500 meters depth near the Canary Islands. Don’t be expecting to see these deep water oddities in your local aquarium store, but take a look anyway because they’re just cool.

There was also this article on a risque new Chimera or Ghost Shark species discovered off the Southern California coast!

As if there wasn’t enough at the beach to look out for as a hazard, people in New Zealand now have to be aware of puffers and puffer toxin when they’re frolicking on those beautiful coasts. This piece should hit home with aquarists, too, as fun and adorable as puffers are there is a risk involved in keeping them in aquariums that has to be kept in mind, as the toxin has the potential inflict some serious damage. Read more on puffer toxin in Eileen’s blog about toxins.

And now for a look at the future of the aquarium hobby! We all know that leaving our precious aquariums home alone for extended periods of time can be stressful, and many of us can relate to the horror of tank disasters that can occur while we’re on vacation or working long hours. Why not construct your own robot to monitor your tank? Seems like an impossibility? Not when it comes with the help of the braniacs at Erector! The Spykee Robot may be the key to giving you a little piece of mind.

This week we got some pretty cool stuff in the fish room in addition to all the favorites. Here are the highlights:

I’m a fan of Possum Wrasses. Also known as Arrowhead Wrasses and Pygmy Wrasses, these little beauties are fun to watch, s and they’re reef safe. Their small size makes them suitable for even smaller tanks. The Tanaka Possum Wrasse is the newest arrival!

We also received a lovely little Polleni Grouper. Only about 3-4″ and very pretty! Of course, I’ve never seen an ugly Polleni.

On the fresh side, the Zebra Loaches that arrived this week are looking particularly robust and active. Those attractive stripes would complement any community tank. The new Bug-eye Squeaker Cats, Synodontis contractus, also caught my eye. Synos are interesting looking cats in general, but the patterns on these are very attractive and the current stock is fat and happy. If you’re on the market for African Cichlids, I recommend the adult Pseudotropheus acei with their spectacular blue color.

Until next time, Patty

Pufferfish image referenced from wikipedia and originally posted by Mbz1