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Author Archives: Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.

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Guppy Love: Hanging with Unattractive Buddies Makes You Look Better!

Guppy varieties

Uploaded to Wikipedia Commons by Melanochromis

A fascinating study at the University of Western Australia has shown that male Guppies (Poecilia reticulata) specifically choose drab-colored “friends” in order to improve their own attractiveness to females. What’s more, the behavior is not instinctive, but rather seems to be learned through experience (via “broken hearts”, I wonder!). This is the first time that any animal has been shown to choose a social group based upon the physical attractiveness of its members.

For Guppies, Appearance is Everything
Female Guppies choose mates based on the brightness of their coloration, with orange being most favored. Researchers presented male Guppies with the choice of 2 groups with which to associate. One group was comprised of a female and numerous drab-colored males, the other a female and attractive males (orange spots covering more than 20% of their bodies).

The test males chose to associate with the drab-colored group. Drab test males were more likely to pay attention to the attractiveness of their male associates. Very attractive male Guppies, it seems, need not worry about such details, as they were “confident” of their abilities to attract a mate regardless of the competition!

Yes, Fish can Learn!
The study, published in the Proceedings of the Royal Society B (V. 280, N. 1756), also confirmed what many aquarists have long suspected – fish can learn and profit from past experiences. Male Guppies raised in isolation from other males exhibited no preferences when given the choice of drab or colorful male associates. Researchers theorize that male Guppies learn to associate with drab companions based on their past mating successes…or failures, as the case may be! Please see the articles linked under “Further Reading” for more on fish intelligence.

Wild guppies

Uploaded to Wikipedia Commons by Per Harald Olsen

Try This at Home
I’ve been able to observe the importance of male coloration in my own aquariums. I have long-established schools of “feeder” (wild type) Guppies in several tanks. Every so often I’ll add a large “fancy” male. Over the next several weeks, that male’s coloration, color patterns and/or fin structure will become very noticeable in the population, despite the fact that there may be 20-40 other males present. Please post your own observations below, thanks.

American Bullfrog

Uploaded to Wikipedia Commons by Ram-Man

Deceitful Bullfrogs
American Bullfrogs exhibit a unique variation of this breeding strategy. Females select mates based upon the sound of the males’ calls, opting to hone in on those made by the largest males. Small males, who seem to know that they cannot attract a mate with their feeble songs, also listen for large males. Known as “satellite males”, the little fellows position themselves at the edge of a dominant male’s territory…far enough from him so as not to be attacked.

From this location they attempt to latch onto females that are swimming in to consort with the larger male. If successful, the satellite male steers his prize away from the larger male’s territory, in hopes of fertilizing the eggs that she is carrying. Although such trickery seems a bit under-handed, it is a good example of the “brains over brawn” concept!

Further Reading
Fish Intelligence: Experiments You can do at Home

Fish Personalities: an Interesting Study

The Best Aquarium Filters for Goldfish


Uploaded to Wikipedia Commons by Heptagon

Although goldfish made their debut as pets over 2,000 years ago, their needs are not always understood by those new to fish-keeping.  Because the average pet store goldfish is small and inexpensive, they are sometimes viewed as “beginner’s pets” that need little care.  Add to this the fact that many people remember “Grandma’s goldfish that lived for years in a tiny bowl”, and it’s easy to see why most meet untimely ends (well-cared for goldfishes can live into their 20’s – and sometimes to twice that age!).  Folks who buy a single goldfish usually do not want to be bothered with a filter, but the lack of filtration is by far the main reason for failure with these otherwise hardy fishes.  However, there is a filter that needs no pad or carbon changes, and which becomes more effective with age – custom made for busy, “filter-shy” fish enthusiasts.  Today we’ll take a look at it and other simple options that will lessen your workload and improve your goldfish’s quality of life.


Goldfish Do Not Stay Small!

When considering a goldfish, it’s important to realize the potential size your pet will reach.  Goldfish are available in a wide variety of colors, 4 tail-shapes, 3 body-shapes and 3 eye-types, but are all of the same species, Carassius auratus auratus.  Those known as comets – the basic pet store or “non-fancy” goldfish – can easily reach 8-12 inches in length.  Sixteen-inch long individuals have been recorded; in fact, I have seen several feral goldfishes near that size in the Bronx River, mixed in with breeding aggregations of carp (I must check if hybridization is possible…).  Fantails, moors and other strains tend to be shorter in length than comets, but they get quite hefty.

Veil Tail

Uploaded to Wikipedia commons by Bechstein


True, improperly-kept goldfishes will become stunted, and may survive in that state for several years, but this is not to be encouraged – and certainly not a lesson to be teaching the children for whom single goldfishes are often purchased.  When fully-grown, your pet will need a 20 gallon aquarium in which to live; plan on a 30 gallon for a pair.


The Ultimate Goldfish Filter

Although now largely-ignored by hobbyists, (perhaps they are “too simple”!), undergravel filters were once considered indispensable by serious aquarists, and are still relied-upon by many public aquariums today.  In zoos and at home, I’ve used these highly-effective filters in aquariums housing creatures ranging from seahorses to alligator snapping turtles, always with great results.


t204151gWhen considering undergravel filters, it’s important to bear in mind that biological filtration – the breakdown (by aerobic bacteria) of ammonia to nitrites and nitrates – is the most important function of a filter (please see article below).  And it is at this aspect of filtration that undergravels excel.  Simply-put, an undergravel filter turns your aquarium’s substrate into a giant, living, biological filtration unit.  What’s more, the filter plate does not take up important living space and, being hidden below the gravel, allows for the creation of pleasing aquascapes.  Best of all, there are no cartridges or filter mediums to clean or replace! 


Water Changes

Regular partial water changes are essential to maintaining water quality and fish health…regardless of tank size, filtration method, or fish species.  When doing partial water changes, be sure to use a manual or battery-operated gravel washer.  In this way, you will remove debris trapped in the substrate along with the water…that’s all the maintenance your undergravel filter will need!


Black Moor

Uploaded to Wikipedia Commons by ﻯναოթ€ռ


Undergravel filters have another characteristic that suits them well for use with goldfish.  Goldfish evolved in slow-moving waters, and they cannot abide fast currents; fantails, lionheads and other round-bellied varieties are especially-weak swimmers.  Yet they produce a good deal of waste, and do best in aquariums equipped with powerful filters (which usually put out strong outflow currents).  Undergravel filters discharge clean water through two tubes that reach to the water’s surface…even when very powerful air pumps are used, outflow currents remain mild.  You can check out a wide variety of air pump styles and sizes here; please post below if you need assistance in choosing a pump.


Increasing Your Filter’s Efficiency

Power heads can be used in place of air pumps if you need to increase water flow through the gravel bed.  You can also set up a reverse-flow system, which will lessen the amount of detritus that becomes trapped in the substrate; please post below for details.


Commercially-available aerobic bacteria (i.e. Nutrafin Cycle) can be used to jump-start your filter or to boost the beneficial bacteria populations that have developed naturally.


Other Goldfish Filters

From simple corner filters to state-of-the art canisters, there is a huge array of other filtering options for goldfish owners.  Please share your thoughts and experiences by posting below.

Further Reading

Aquarium Filtration: Understanding the Nitrogen Cycle

Making the Most of Undergravel Filters

Synodontis Angelicus Catfish – The Most Spectacular Synodontis

Synodontis Angelicus Catfish

Uploaded to Wikipedia Commons by Haps

Faced with “an embarrassment of riches”, catfish enthusiasts usually find it impossible to single out a favorite species.  Those in the genus Synodontis – boldly-marked and fascinating to observe – are a case in point.  Each time I’m introduced to a new species, I find some quality that draws me to learn more about it.  But if the Angelicus Squeaker, Synodontis angelicus, is not the most sought after of all Synodontis cats, it certainly is in the running.  Also known as the Black Clown Catfish, Angelicus Synodontis, Polka-Dot Synodontis and Angel Squeaker, it is both breathtakingly-beautiful and extremely interesting in its habits. And dedicated aquarists have the opportunity to broaden our understanding of the little-studied species, as captive breeding success has remained elusive.



The Angelicus Squeaker’s jet black, dark gray or deep purplish coloration is beautifully offset by numerous yellow or white spots.  Some have described it as having the opposite color pattern of another popular relative, the Cuckoo Squeaker, S. multipunctata (please see photo below).  Color and spot patterns vary greatly, and individual fishes are capable of radically changing their background colors.  Health, stress, age, sex and other factors are likely involved, but much remains to be learned.  Fishes involved in aggressive encounters or, perhaps, courtship, sometimes lighten to almost white in color.


The maximum size reported is 9.4 inches, but detailed field surveys have not been carried out, and there are rumors that much larger individuals have been seen.  Growth appears to be rather slow, at least by pet catfish standards.


Synodontis mltipunctatus

Uploaded to Wikipedia Commons by Mario Rubio García

Natural History

This river-dwelling catfish has a large range, but details concerning its exact distribution are sketchy.   It is known to occur throughout much of the Congo Basin, and has been reported from Cameroon, the Democratic Republic of the Congo and the Congo Republic.


The Synodontis Aquarium

Angelicus Squeakers remain rather subdued during the day, unless food is detected, but they are very active by night.  Although success has been had in smaller accommodations, I believe it best to plan on a 55 gallon aquarium for 1-2 adults.


Angelicus will not thrive if forced to remain in the open.  As they can be quite picky when it comes to choosing a hideaway, a variety of caves, hollow logs, driftwood refuges and similar structures should be provided. .  This is even more important when 2 or more Angelicus Squeakers are housed together, as battles over favored hiding spots are common.  Once a retreat is chosen, your fish will likely remain faithful to it.


Additional security in the form of well-rooted live or artificial plans should also be added.  Fishes kept in complex environments will exhibit a greater variety of natural behaviors than those denied access to hiding places…you’ll wind up seeing of your fish, and more of interest!


I like maintaining this and similar Synodontis cats on sand, as they keep very active by rooting about for food.  If displaced sand causes problems in your aquarium, they will also do well on smooth gravel.



Temperature and pH

Temperatures of 74-80 F and a pH range of 6.0-8.0 have been used successfully.  I have found 78 F and pH 7 to be ideal.


Several friends working in public aquariums and for fish importers have reported seeing what appear to be heater burns on Angelicus Squeakers.  I have not seen this in my collection.



I’ve successfully kept groups of 6-8, but they must be watched carefully, especially at night.   Angelicus Squeakers guard their caves, and we know little about male-male rivalry or aggression that may occur when pairs are courting.


They may also be kept with similarly-sized peaceful or moderately aggressive fishes of other species. Active top-feeders will out-compete most catfishes for food, so night-feeding and other accommodations to bottom-feeders will be necessary.


I’ve not tried hosing Angelicus with other catfishes, and, in most situations, would avoid any fish that is dependent upon caves for shelter.



Angelicus Squeakers are opportunistic feeders that will readily consume all manner of flake, pelleted and frozen fish foods.  Mine especially relished crushed crickets, blackworms and fresh and freeze-dried shrimp.


Plant-based foods are also important.  Cucumber, zucchini, spirulina tablets and similar foods should be offered regularly.


Individuals maintained on flakes and pellets alone do not do as well as those provided a diet comprised of live and frozen invertebrates.


Breeding Synodontis Angelicus Catfish

Despite the high demand for these beautiful fishes, captive breeding has not been documented, and little is known of their reproduction in the wild (other than that they are egg-scatterers).  Eggs have been produced by Angelicus Squeakers in several private and public collections, but none have hatched.  Anecdotal reports hint that hormone-based breeding has been accomplished in Europe, but details are not available.

I’m sure that the key to success lays in a detailed study of their natural habitat…pH, temperature or water level changes may be involved. Where captive spawning has occurred, hatching failures may possibly be linked to nutritional deficiencies. Increased amounts of live and protein-rich foods were offered prior to spawning in some cases.  Please let me know your thoughts (or, hopefully, successes!) on this important topic by posting below.

Further Reading

Keeping the Frog Mouth Catfish

Keeping European and Oriental Weatherfish


New Fish Species in 2013 – Sharks, an Antarctic Monster, and More


Uploaded to Wikipedia Commons by LT DeeDee Van Wormer

Even considering that new fishes are discovered at the rate of nearly two per week, 2013 was a spectacular year for fish enthusiasts.  Included among the undescribed new fish species brought to light in 2013 were several relatives of common marine and freshwater aquarium fishes, numerous sharks (including a large hammerhead off South Carolina), a knife fish that utilizes a different type of electric current than all others, a bizarre beast from the depths of the Antarctic’s Ross Sea, one of the world’s smallest vertebrates, and one of the world’s largest freshwater fishes.  The diversity of these new species is staggering, and all seem to have amazing traits, so I was hard-put to select my favorites.  Please be sure to share information about those that caught your eye by posting below.


Giant Oarfish, Regalecus glasne

The Giant Oarfish is not a newly-discovered species…in fact, it has been inspiring tales of sea serpents for thousands of years.  But despite being the world’s longest boney fish, this 30+ foot-long behemoth is so rarely seen that I felt compelled to mention it here.  Fish-watchers were quite surprised when two individuals washed up off southern California in less than a week…and both were in great condition.  Measuring 14 and 18 feet long, one contained hundreds of thousands of eggs, while the other was infested with large tapeworm-like parasites.


Arapaima leptosoma

Uploaded to Wikipedia Commons by George Chernilevsky

Arapaima, Arapaima leptosome

At a weight of over 400 pounds, South America’s air-breathing, torpedo-shaped Arapaima is one of the world’s largest freshwater fishes.  It was not until 2013 that ichthyologists learned that a second species was “hiding in plain sight” (in commercial aquariums, even!).  Distinguishing the new species is important, as Arapaima have been hunted to near extinction across much of their range.  Slight differences in the natural histories of the two species may help us to understand how best to conserve them.


Blue-Bellied Night Wanderer, Cyanogaster noctivaga

The fish bearing this long name is, at 0.68 inches in length, one of the world’s smallest vertebrates; it misses being the world’s tiniest fish by a mere 7mm.  Size was not all that helped to keep this fish hidden for so long…it is also transparent and nocturnal, and “wanders” in the tea-colored waters of the Rio Negro.


Hopbeard Plunderfish, Pogonophryne neyelori

This fish’s appearance is stranger than its name.  Looking like a cross between an Oyster Toadfish and a tadpole, the Hopbeard Plunderfish was hauled up from 4,560 feet below the surface of the Antarctic’s Ross Sea by Ukrainian commercial fisherman.  As you can well imagine, we know nothing of its natural history (and, I’m guessing, may not for some time!).


Long tailed Carpet Shark

Uploaded to Wikipedia Commons by EurekAlert.org

Long-Tailed Carpet Shark, Hemiscyllia Halmahera

This 28-inch-long, attractively-marked shark is related to the Epaulette or “Walking” Sharks, several of which are popular in the aquarium trade.  A flexible body and leg-like pectoral and pelvic fins allow it to prowl about tide pools and submerged rocks in search of marine worms, crabs and shrimps.  Western Australian Museum ichthyologists discovered it off the East Indonesian island of Ternake, which is part of the Maluku Island chain.


Bluntnose Knifefish, Brachyhypopomus bennetti and walteri

Knifefishes, several of which are popular in the aquarium trade, are known to use electric currents to assist in navigation.  One species, the misnamed “Electric Eel”, also uses electricity to both hunt and defend itself.  The newly-described species emit electric currents from an organ in the tail.  Like all other electric-producing fish, B. walteri  releases alternating positive and negative pulses.  B. bennetti, however, is unique in that it produces only a direct, one phase current.  This fish lives below floating weed masses in Brazil, and seems especially prone to losing part of its tail to predators.  The navigational abilities of knifefishes that produce alternating currents are severely hampered if they lose a portion of the tail.  However, B. bennetti seems not to suffer when the tip of its tail is lost, as the direct current it produces functions just as well…an amazing adaptation if ever there was one!


More Sharks Discovered in 2013

The 8-12-foot long Carolina Hammerhead, Sphyrna gilbert resembles the better-known Scalloped Hammerhead, but is genetically and structurally distinct.  It is the largest fish to be found in such a developed area (inshore, off South Carolina) this year.


Sawsharks resemble sawfishes.  Their “saws”, which bear barbels at the half-way point, are used to disable the fishes upon which they feed.  The new species discovered in 2013, Pristiophorus lanae, hails from the Philippines.  Little is known of its natural history.


Further Reading

2012’s New Fish Species

2010’s Most Unique New Fishes


The Best Holiday Gifts for Aquarium Owners, Tropical Fish Hobbyists & Fish Geeks

Today I’ll highlight some fish-keeping items that I’d be pleased to give or receive as holiday gifts. For the most part, I’ve focused on Reverse Osmosis Systems and Ultraviolet Sterilizers, both of which lessen our workload while enhancing fish and invertebrate survival.  I was first introduced to these tools while working in zoos and public aquariums, and am happy to see that reasonably-priced models are now available for home use.

tPG01062Reverse Osmosis Systems

I first began working with reverse osmosis (RO) systems about 15 years ago, while trying to correct water quality problems that plagued the amphibian collection at the Bronx Zoo.  Those I used were effective, but also huge, complicated, and difficult to maintain…I hated them!  Today’s home units are much more user-friendly; instruction manuals are posted online (please see links to individual products below), and customer support is readily available.
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