That Fish Blog – Aquarium Advice and Information

Large, flashy, uniquely-shaped and active, Silver Monos, Monodactylus argenteus, always draw attention when seen for the first time.  But there are many misconceptions concerning their proper care, and new owners often become frustrated with them and move on to other interests.  However, when their unique needs are met, Monos are quite hardy and make for spectacular exhibits.  A group I cared for at the Bronx Zoo, housed with Mudskippers, Fiddler Crabs and Banded Archerfish, proved so interesting that they rivaled neighboring Leaf Insects, Hornbills and Tapirs for visitors’ attentions.

Uploaded to Wikipedia Commons by Brocken Inaglory

Description

The Mono’s silvery coloration shimmers under light, and is nicely offset by yellow or black fin tips and the jet-black stripe that runs along the edges of the dorsal and anal fins.  The body is flattened and disc-shaped, and the sturdy dorsal and anal fins are much-elongated.  Silver Monos are powerful swimmers, well-able to buck the strong currents common to the tidal rivers and coastal mangroves that they frequent.  If given enough space and a proper diet, they can reach 9- 10 inches in length, but most in the pet trade top out at half that. Read More »

Most goldfish owners have encountered fish that suddenly become unable to submerge.  Try as they might, they float, often belly-up, at the surface, and seem to be in great distress.  Less often, the hapless victims may be unable to rise to the surface, or may swim in an “off balanced” or head-down position.  Fantails, Orandas and other strains with rounded bodies are the most common victims, but Comets and others are not immune.  The problem is also frequently seen in Bettas, or Fighting Fishes, but may afflict any species.  Swim Bladder Disease almost always involved.  This condition is actually a general term applied to a wide variety of ailments, rather than a specific disease per se.  Today we’ll look at its causes, prevention and treatment.

Uploaded to Wikipedia Commons by Humanfeather / Michelle Jo

The Swim Bladder

The swim bladder is a sac-like organ located in the abdomen of most bony fishes, but is absent in the cartilaginous fishes (sharks, rays and their relatives).  The lining of the swim bladder, and the many blood vessels that transverse it, allow gasses to be passed into and out of the organ.  Goldfishes and certain others are also able to exchange gasses through a duct or opening in the bladder that leads to the esophagus.  In this manner, fishes control their buoyancy, or ability to float and move up and down in the water column. Read More »

Many years ago I established a school of 75 Boezeman’s Australian Rainbowfish (Melanotaenia boesemani) at the Bronx Zoo.  The exhibit, which they shared with mangrove snakes, land crabs and crayfishes, made for a stunning display.  And although the building also housed proboscis monkeys, marsh crocodiles, hornbills and other impressive beasts, the brilliantly-colored Rainbowfishes drew a great deal of attention from visitors.

But many keepers become disappointed when, after a time, their fishes’ fading colors do a disservice to the “rainbow” part of their name.  Based on experience with related species, I’ve always provided my Rainbowfishes with highly varied diets, in which insects were heavily featured.  Those under my care have usually retained their bright colors, and breeding has been consistent.  A recent study that examined the natural diet of wild Rainbowfishes seems to bear this out, and has important implications for the care of other species as well.

Uploaded to Wikipedia Commons by Roan Art

Terrestrial Insects: an Overlooked Food Item

My lifelong observations of captive and free-living fishes have led me to conclude that land-dwelling insects play an important role in the diets of many freshwater fishes.  As anyone with a pool or outdoor pond can imagine, untold numbers find their way into fresh and marine waters each day.  In 2009, the research of National Oceanographic and Atmospheric Administration biologists revealed that terrestrial insects comprise up to 100% of the diets of some US fish species. You can read more about this topic in the articles linked below. Read More »

 In habits, appearance, and evolutionary history, the African Butterfly Fish, Pantodon buchholzi, is one of the most unusual of all aquarium species.  Yet despite having been in the trade for over 100 years, this “freshwater flying fish” (a misnomer, see below) gets little attention.  Captive breeding is challenging but possible, and its fantastic hunting behaviors are thrilling to observe.  I helped to set up an African Butterfly Fish exhibit at the Bronx Zoo, and was not at all surprised when it became a great favorite.  Most of the visitors I spoke with were astonished to learn that such an “exotic” creature, worthy of a large zoo exhibit, was available at many pet stores! 

Description

The yellowish-green to silvery-tan body is marked with an intricate pattern of speckles and lines.  The huge pectoral fins, reminiscent of those of marine flying fishes, lend an uncanny resemblance to a dead, floating leaf when viewed from above.  Long rays extending from the tail and the pelvic fin add to its remarkable camouflage.

Uploaded to Wikipedia Commons by Toniher

The African Butterfly Fish’s mouth is noticeably upturned, an adaptation for feeding on insects at and above the water’s surface.  Less noticeable is the mouth’s large size and the many teeth it bears; although it tops out at 5 ½ inches, this specialized predator can take quite sizable insects and fishes.

Utilizing its wing-like pectoral fins and unique musculature, the African Butterfly Fish can explode from the water’s surface to snatch low-flying dragonflies, moths and other insects, and to escape predators.  It does not, as far as we know, glide above the water as do marine Flying Fishes (please see photo). Read More »

Shrimp of various species play an important role in the natural diets of many freshwater fishes, and the nutrients they supply differ from those found in insects and other more commonly-used aquarium foods.  Many native and exotic fishes under my care at home and in zoos prefer shrimp to all else, and do well when they are added to the diet.  And while ocean krill (not a true shrimp) is readily available, I wonder about the long range effects of feeding a marine animal to freshwater fishes.

Unfortunately, freshwater shrimps are difficult for the average aquarist to procure. I was, therefore, pleased when Zoo Med began offering canned freshwater shrimp.  Although marketed as a reptile food, I have fed canned shrimp and find them to be some of the best foods for freshwater aquarium fish, showing great results.  But I’ve been remiss in spreading the word among my hobbyist friends…if you decide to give them a try, please post your thoughts below, thanks.

An Important Consideration                                                                         

Small, whole animals are used in Zoo Med’s canned freshwater shrimp product.  This is preferable to offering our fishes small pieces of food market marine shrimp, which are usually missing nutritionally valuable internal organs (note: food grade shrimp are fine to use on occasion). Read More »