That Fish Blog – Aquarium Advice and Information

Seahorses have much to attract aquarists – armor plated and prehensile tailed, and with independently-moving eyes and wing-like fins, they can also change color as well as grow and discard filamentous appendages. And, of course, the males become “pregnant”.

My first contact with seahorses came in the mid 1960’s when my grandfather, long in awe of these unusual fishes, mail-ordered a group of dwarf seahorses, Hippocampus zosterae, from a dealer in Florida. The shipment included several males carrying eggs, and I was hooked – so much so that I wound up writing a book on seahorses.

Texas A&M researchers are now learning the male seahorse’s pouch is far more than a mere container for eggs, and are trying to discover just how such a unique organ managed to evolve. Tissue from within the pouch actually grows around the eggs and functions in a similar manner to a mammalian placenta. Through it the seahorse father is able to keep blood flowing around the eggs, and to provide them with oxygen and nutrition. Amazingly, he also makes minute adjustments to the salinity of the water within his pouch, gradually increasing it as the embryos’ needs change. By hatching time, the salinity of the pouch water matches precisely the salinity of the surrounding ocean.

The male seahorse fertilizes the eggs once they have been deposited into his pouch by the female. From that point on, the reproductive roles of the sexes are reversed. The researchers at Texas A&M are also looking into the effect this has had on mate selection and other aspects of seahorse reproductive behavior. In certain species of pipefish (close relatives of the seahorses) females have the bright coloration usually associated with male fishes, and they compete for access to the egg-incubating males. Seahorses are, as far as we know, monogamous. They form long-term pair bonds which are reinforced, in many species, with daily “greeting” rituals (the pair clasps tails, swims together, etc.), but much about how role-reversal has affected mate selection is unknown.

In other related news, the Georgia Aquarium has announced that one of its male weedy seadragons is carrying eggs, only the third time such has been recorded in a US aquarium. Weedy seadragons, and the larger and even more flamboyantly decorated leafy seadragons, are close relatives of the seahorses and pipefishes and also exhibit similar reproductive strategies.

You can read more about the Georgia Aquarium’s seadragon breeding program and see a seadragon video at:
http://www.georgiaaquarium.org/exploreTheAquarium/webcam-seadragon.aspx.

Please also take a look at my seahorse book if you have a chance (see above) – I would greatly appreciate your feedback.

I’ll write more about keeping seahorses and their relatives in aquariums in the future. Until then, please forward your comments and questions.

Thanks, Frank.

In the wild, weatherfishes spend a good deal of time buried in the substrate, with just their heads protruding. In contrast to most other burrowing fish, they become quite bold in the aquarium and quickly abandon their secretive ways. Still, a soft substrate is appreciated, and it is quite amusing to see them burst forth from the sand when they detect food. I suggest Aqua Terra sand. If you do use gravel, be sure it is a smooth variety, such as walnut gravel, so that the delicate skin will not be damaged.

Always hungry, weatherfishes spend a good deal of time foraging – and in doing so are likely to uproot growing plants. However, well-rooted aquarium plants should be included in the aquarium when possible, as the fish seem to favor resting among plant leaves and stems.

Although weatherfishes get along quite handily without much aeration, their tank should be have a good aquarium filter as these ravenous feeders produce a good deal of waste.

Temperature and Other Water Parameters
The European species is adapted to cool and cold climates, and does best if water temperatures are kept below 75F. Oriental weatherfishes are far more adaptable, and inhabit areas where the water temperatures range from 36 -86F. They become inactive when temperatures dip below 50F or so, and are best kept at 66-75F.

Weatherfishes are undemanding as regards pH and water hardness, but do best at a pH of 7 or slightly below and in soft water.

Feeding
Weatherfish do a fine job of consuming food missed by tank-mates. Armed with sensory barbels, they miss little and will even root below gravel and rocks for food trapped there. However, they have quite large appetites and should by no means be expected to get by on leftovers.

Both species do best when offered a variety of foods. Although primarily carnivorous, weatherfishes should also be given food preparations that contain some plant material, such as flake fish food and Tetra tablets. A variety of freeze dried fish food, such as bloodworms and krill, should also be offered.

Free-living weatherfishes feed largely upon insects and other invertebrates, and captives do best when given ample live food. They particularly favor crushed crickets, blackworms, brine shrimp and small earthworms, and will take bits of fish and wild-caught insects as well. I have kept a number of individuals of both species for decades (see below) and attribute some of my success to a diet high in a variety of live foods.

Social Grouping/Compatible Species
Weatherfishes seem quite social by nature, and often rest in physical contact with others of their kind. You may even see them “exploring” one another with their barbels. They are sturdy enough to be kept with fairly large fish, and do not bother smaller animals (however, they will consume fish eggs and, possibly, fry). I have successfully kept them with fairly aggressive animals such as American eels and African clawed frogs without incident.

Captive Longevity
An Oriental weatherfish in my collection lived for 21 years. Longevities of 10-15 years are regularly reported.

Breeding
Breeding can be induced in both species by gradually lowering the water temperature to 60-65F while simultaneously dropping the water level to ½ the usual level and shortening the light cycle to 8 hours. After 2-4 weeks (longer periods may be required by fish from certain populations), water of approximately 10F warmer than ambient should be added to raise the water level back to normal. The temperature should be maintained at 72-75F and the light cycle increased to 14 hours.

The greenish eggs are attached to plants and the substrate following a “mating dance” of sorts. The males, distinguishable by their slightly larger and triangularly shaped pectoral fins, fertilize the eggs externally. It is best to remove the eggs (or adults) for hatching, which occurs in 3-5 days. The fry readily accept Daphnia, newly hatched brine shrimp prod, chopped blackworms and other live foods, and there are reports that they will take flake fish food and finely chopped frozen bloodworms as well.

Miscellaneous
Weatherfishes are exceptionally responsive to food and take readily to hand feeding – they will even wiggle onto a palm held partially out of water for a favored treat. To encourage hand feeding, try using freeze-dried or fresh prawn.

As mentioned in Part I of this article, I have encountered Oriental weatherfishes of 12-13 inches in food markets in two of NYC’s Chinese communities. The fish I found were in poor shape, but you may wish to keep an eye out for others in food markets – those I saw were much larger than pet trade animals, and would have made spectacular additions to any collection.

Please be aware that weatherfishes, like eels, catfishes and other scale-less species, are sensitive to many fish medications. Be sure to read the label carefully, or write in to this blog for more information.

I look forward to hearing about your experiences with weatherfishes, and to addressing any questions you might have. Thanks. Until next time, Frank.

Further information about weatherfishes is available at:
http://www.fishbase.com/Summary/speciesSummary.php?ID=3016&genusname=Misgurnus&speciesname=anguillicaudatus

Overview
Weatherfishes do not receive nearly the attention they deserve from aquarists, often being purchased as “curiosities” or “scavengers”. This is unfortunate, as they are among the most interesting of all fishes, and are very hardy as well. Their inquisitive dispositions and readiness to feed from the hand can only be described as “charming”. In part 2 of this article we will learn more about how to keep and enjoy them in the aquarium.

Two species are regularly available – the European weatherfish and the Oriental weatherfish (also sold as the dojo loach or Japanese weatherfish). The Oriental weatherfish is more commonly seen in the pet trade in the USA.

Physical Description
Weatherfishes have elongated, eel-like bodies with 5 pairs of fleshy barbels (sensory organs) surrounding the mouth. Their color ranges from metallic and golden tan through various shades of brown. The European species is striped, while the Oriental weatherfish is largely spotted, but both exhibit a mixed pattern of these markings. The Oriental weatherfish is also available in gold and albino color morphs.

Each can reach 12 inches in length, but rarely exceed 8 inches in the aquarium. I at first thought this was be due to a poor diet, i.e. their having to subsist upon “leftovers”. However, a number of individuals of both species that I have kept (including an Oriental weatherfish that reached age 21) also topped out at that length, despite being fed a diet rich in insects, snails and aquatic worms. I did see animals of 12-13 inches in a food market in a Chinese community in NYC. I was told that they had been imported from Hong Kong, but the store owner did not know whether they had been wild-caught or farm-raised. Perhaps, as with other fish species, local populations or races vary greatly in size.

Weatherfishes are classified as loaches, in the family Cobitidae. Many of the 118 species in this family of fresh water fishes, including the coolie loach, clown loach, yo-yo loach and hill stream loach, are popular with aquarists.

Range and Habitat
Both species have a huge range and are equally at home in many types of waterways. The European weatherfish favors rivers, streams and lakes, but is able to tolerate farm ponds and other less-than-ideal habitats as well. The Asian species is found in every type of fresh water environment imaginable. Due to its ability to take oxygen from the air, it is found in stagnant waters and does quite well in swamps, ditches and rice fields.

The Oriental weatherfish occurs from southern Russia south through India and China to Vietnam, Korea and Japan and has been introduced to Australia, Germany, the Philippines, Palau and the USA (Hawaii, California, Idaho, Indiana, Illinois). Much to the horror of loach fanciers, it is used as fish bait in some places, a fact that may in part account for the widespread feral populations. Detailed fieldwork has not been carried out with regard to introduced populations. However, as ravenous predators of invertebrates and fish eggs, it is suspected that they are negatively affecting local species. For this reason, weatherfishes are illegal to possess in Australia and England.

The European species occupies most of Europe except for Great Britain, Ireland, Scandinavia and Greece. Introduced populations have been found in Italy, Spain, Croatia and the USA (Great Lakes region and possibly elsewhere).

Diet
Both species feed largely upon insects, snails, worms and terrestrial invertebrates that fall into the water. They will also feed upon carrion and likely take fish eggs and fry as well.

Reproduction
Rising temperatures and water levels stimulate breeding in both species. Pairs perform “mating dance” of sorts during which the male wraps himself about the female and fertilizes the eggs as they are laid. The eggs are greenish in color and attach to plants and the substrate. No parental care is provided.

Miscellaneous
The weatherfish owes its common name to its unique habit of becoming very active just before a storm. This activity apparently is caused by the effects of barometric pressure (change in air pressure) upon the swim bladder. Weatherfish are among the earliest fish species to have been maintained in captivity – farmers in medieval Europe kept them for their weather predicting abilities, and in Japan they were much valued for their habit of swimming to the water’s surface prior to earthquakes.

Weatherfishes can breathe atmospheric oxygen, a facility that allows them to survive in swamps, rice fields and other habitats unsuitable for many fishes. Interestingly, they have evolved a respiratory system that is quite different than that employed by the “labyrinth breathers” (gouramis), lungfishes and other species that utilize air-borne oxygen. When breathing from the water’s surface, weatherfishes gulp air, absorb its oxygen within the gut and expel the excess via the anus.

During droughts, both species aestivate by burrowing into the mud, where they survive without water for quite long periods. Weatherfishes living in temperate areas spend the cooler seasons below the mud as well.

Please write in with your questions. I am very interested in hearing from you concerning the sizes your weatherfishes have reached, or if you have observed large individuals in food markets. Thanks, Frank.

An interesting article about introduced populations of the Oriental weatherfish (here and abroad) is posted at:http://www.thefreelibrary.com/New+records+for+the+alien+oriental+weatherfish,+Misgurnus…-a0162455040

Please welcome back Frank Indiviglio with another article.

Those of you who use blackworms as fish or amphibian food have likely been surprised (or horrified!) to find small leeches in among the worms. My own curiosity and questions from others led me to take a closer look. Upon doing so, I was amazed to see the leeches sucking down the blackworms like spaghetti!

Leeches are, of course, best know for their blood-sucking ways – but it turns out that a great many of the over 650 species are actually predatory (although the largest, the giant Amazon leech, Haementaria ghilianii, does suck blood – and, at 12 inches in length, quite a lot of it!). Blood sucking forms, it seems, evolved from predatory leeches.

I established a colony of the leeches in an aquarium and found them to be exceptional scavengers (as are blackworms themselves). They emerged from the gravel bed at night (they are sensitive to light – I was able to best see them by using a night viewing bulb) and made short work of dead fishes and leftover food, and were very effective at reaching areas below rocks and the filter. They showed no interest at all in the loaches, African clawed frogs, snails or shrimp that shared their aquarium (at least while the foregoing were alive!). The leeches deposited their eggs in a case attached to the undersides of rocks. The egg case’s covering is tough and leathery, and obviously offers good protection against predators.

I believe it would be worthwhile to investigate the use of this leech as an aquarium scavenger. I am still uncertain as to the species, and had one unexplained die-off, and so would greatly appreciate hearing from anyone who might have further information. Thanks. Until next time, Frank.

General information on leeches is available at:
http://www.austmus.gov.au/factSheets/leeches.htm

Thanks Frank!

Dave

Today I’d like to introduce you to the maintenance of cold water aquariums, a fascinating but often overlooked branch of aquarium keeping focusing on marine and freshwater fishes and invertebrates from temperate regions.

Exotics Close to Home
Please don’t be misled into equating exotic and interesting creatures with “far-off, tropical places”. Shorelines, ponds, tidal pools and rivers throughout the world’s temperate regions (with the exception of extreme s. Florida, the entire USA is in the temperate zone) yield animals of unimaginable variety and interest. While it is true that many of the most spectacularly colored fishes are found in the warmer parts of the world (their bright colors likely help males and females of the same species recognize each other among the great diversity of similar species in the tropics), breeding males of many temperate fish species, i.e. the sunfishes, do rival those of their tropical counterparts.

Why keep Temperate Fishes and Invertebrates?
Animals from temperate areas offer many advantages to aquarists who live in the USA. Often, our normal seasonal rhythms of temperature and light fluctuation are sufficient to encourage such creatures to exhibit natural behaviors, and even to breed. Also, it is often easier for us to provide a wider range of foods and a more natural environment for them than we can for creatures from faraway places. In some cases, where legal, we may even be able to collect and keep native fishes and invertebrates.

Creating Natural Habitats
If you live near a body of water, try to observe firsthand the environments and habits of a variety of aquatic creatures. You might consider modeling your aquarium after a particular habitat — a tide pool, a weedy, fresh-water pond, or a river bed, for example. Take note of the local substrates, rocks and other natural items and purchase similar ones when setting up your tank prod (collecting natural substrates is risky, due to the possibility of mineral, pesticide or other chemical leaching).

Heat
Cold water aquariums are maintained in a similar fashion to tropical aquariums, but we must consider the effects of heat. Many animals from temperate regions are very sensitive to rising water temperatures and to the lower oxygen levels that accompany them. You may, therefore, need to install a chiller to moderate temperatures during the summertime.

Species to Consider
Some of the animals that I have maintained with success in cold water aquariums, and which I plan to cover in future additions to this article, include American eels, fifteen-spined sticklebacks, pygmy and other sunfishes, mantis shrimp, sea stars, Chinese sailfin suckers, weather fish, horseshoe crabs, blue claw crabs, bullheads and madtoms, white clouds, various snails, crayfish and shrimp, giant water bugs and other aquatic insects and many others.

I’ll now give a quick overview of two unusual animals – the oyster toadfish and the spider crab – which are easily maintained in unheated marine aquariums. I’ll cover their husbandry in detail in future articles.

Oyster Toadfish, Opansus tau
This unusual marine fish, ranging down the Eastern Seaboard from Maine to Cuba, seems to cross the line between fish and amphibian – its face even resembles that of a toad. In addition, toadfishes produce sounds audible above the water and certain Asian species can travel overland for considerable distances.

Oyster toadfishes will become quite tame in captivity, and, given a tank of 55 gallons or so, may well breed. Males are ferocious guardians of their eggs, and have been known to stay with nests that are exposed at low tide.

Oyster toadfishes have survived for 15 years in captivity, and will accept nearly any meat-based frozen or pelleted food as well as live shrimp, small fishes and worms. They learn to associate their owners with food, but will bite when handled, and the spines that can inflict painful wounds.

Atlantic Spider Crab, Libinia emarginata
Spider crabs, common yet fascinating if you take the time to know them, are members of a family which includes the Japanese spider crab. With legs spanning 8 feet, these giants awed me when first I observed a large group in a pubic aquarium in Osaka, Japan. American aquariums now exhibit them as well – trust me, they are well worth the trip.

The Atlantic spider crab is a valuable aquarium scavenger, and, using its tiny pointed claws to probe into nooks and crannies, misses little. Younger animals have the endearing habit of jamming algae and vegetation into the crevices of their shells, taking on the appearance of a “walking plant”. They will also nibble at this portable garden from time to time. I have found that they forgo this habit when they reach a carapace size of about 3 inches, although I have yet to discover why.

Spider crabs rarely bother tank-mates and readily consume fish flakes, pellets, blackworms, frozen food fish foods, algae and green leafy vegetables.

In the next installment of this article I’ll write about temperate, fresh water animals that are readily available in the pet trade. Until then, please write in with your questions and comments. Thanks. Until next time, Frank.

Information on the natural history of the oyster toadfish, along with a photo, is available at:
http://fishbase.mnhn.fr/Summary/SpeciesSummary.php?id=3069&lang=Portuguese