That Fish Blog – Aquarium Advice and Information

Hey Fish Blog Followers! There are lots of different types of freshwater communities created by hobbyists. Some people choose a peaceful community of tetras and other small docile fish, while others opt for a tank populated with predators or other territorial species, often a fine balance between tolerance and aggression. Many aquariums are somewhere in between, referred to as semi-aggressive communities, which often include fish such as barbs, gouramis, large tetras and others that fit into the category.  Today I wanted to give a small introduction to several popular species of fish often purchased for these aquariums that may interest you.
 

Not Exactly Maneaters

Some of the most popular fish for the freshwater semi-aggressive community are the cyprinids known as sharks. These are not the cartilaginous carnivores as featured in movies or the Discovery Channel. These fish are found primarily in the waters of Southeast Asia and Thailand. There are several species that are often imported for use in the aquarium trade, and several species also referred to as sharks that are less common in the trade. Though from several different genera, these fish all have in common the pointed heads and large, curved dorsal fins that give them their misleading common names.

Though these fish lack teeth, as a general rule they are considered semi-aggressive, if not for the sizes they attain, then for the territoriality they often express as they mature. They are generally not suitable for tanks under 55 gallons (some not less than a 75 to 100 gallon tank) and should only be mixed with fish that can stand up to the potential for chasing and harassment that sharks can dish out (especially to their own kind). Smaller fish may eventually be seen as a snack as the fish grow. Sharks make bold and interesting additions to freshwater semi-aggressive communities, as long as the tank is of adequate size and the conditions in the tank suit their needs. Suitable tank mates for most include fish like barbs, catfish, large tetras, and other fish of similar temperament.

If you are considering the addition of a shark to your community, there are several things to keep in mind. As far as the set-up goes (besides having an adequately sized aquarium) be sure that you provide plenty of cover like wood, plants or rock formations so these fish can hide and fell secure when they feel the need. A tightly fitting lid is also highly recommended as they tend to be terrific jumpers, especially if startled. Most common sharks prefer well-aerated, clean water with temps between 74 and 81 degrees (F) and a pH maintained between 6.5 and 7.5. Sharks do not tend to be finicky eaters, readily accepting flakes, pellets and frozen, freeze-dried or live treats like bloodworms, tubiflex, glass worms, plankton, brine shrimp or other meaty tidbits.

Popular Species

There are several species of freshwater shark, and variants of these species, regularly available on the market that may be candidates for your semi-aggressive community.

Bala Sharks (Balantiocheilus melanopterus), also called Tricolor Sharks, are a popular variety with silvery scales and bold black edges on the fins and tail. Though attractive, this species tends to be rather skittish unless kept in small groups. These fish tend to be more shy and docile than many of the other sharks. Reaching a length of between 13 and 15 inches potentially, this species is best left to aquarists with tanks of at least 75 gallons or more for a single specimen, much larger if they are to be kept in the security of a small group.

Rainbow Sharks (Epalzeorhynchos frenatus) may be the best choice for most hobbyists, despite their tendency to become territorial and increasingly aggressive as they mature. Also known as the Ruby Shark or the Red-Finned Shark, this species grows to only about 6 inches and bears bright red fins that are quite attractive. Several variants have also been selectively bred to make things even more interesting, such as albinos and white-finned. These sharks should be kept as a single specimen in the community as they do not tend to tolerate others of their kind in the confines of an aquarium. Red-tail Sharks (Labeo bicolor) are similar in size and behavior to Rainbow Sharks, but lack the red fins and display a velvety black body and a red tail.

Other types of freshwater sharks include Black Sharks, Iridescent Sharks, Colombian Sharks, and others that are even more uncommonly seen in the trade. For various reasons, these species are typically not suitable for the average semi-aggressive community, and careful consideration should be taken before purchasing these species.

Black Sharks are attractive, but they grow rather quickly to about 30 inches in length, too large for most home aquariums. Iridescent Sharks are actually a type of catfish that also quickly grows from a 2 inch juvenile to lengths nearing 4 feet, another that should not be considered for the average home aquarium. Colombian Sharks are sleek and active catfish too, rounding out at about 10 inches, with huge appetites and a preference for brackish to marine conditions as they mature.

Thanks, hope this information is helpful!

Patty

Hello, Frank Indiviglio here.  As a child, I constantly combed the pet stores of the Bronx and Manhattan in search of the odd catfishes, lungfishes and eels I so favored.  I distinctly recall first coming upon some creatures labeled as “rubber eels”, and realizing that I was looking at something special – I just didn’t know exactly what!  The blue-gray “fish” were indeed quite rubbery in texture and did look like eels, yet something was “off”.  In time, I learned that these odd beasts were amphibians, specifically aquatic or River Cauca Caecilians, Tylphlonectes natans.

Natural History

Today, so many years later, you can still find these caecilians being sold as rubber eels.  The River Cauca caecilian is one of the few aquatic members of this little studied amphibian order (the Gymnophiona), and, even now, is the only one to regularly appear in the trade, or even in zoos.  They are found only within the drainages of 2 rivers systems in northern Columbia and northwestern Venezuela, and little is known of their lives in the wild.

Aquatic Caecilians in the Aquarium

River Cauca Caecilians are quite hardy when given proper care, and may even surprise you with young, which are born alive and have external gills.  I’ve bred them in a well-filtered (undergravel) 20 gallon aquarium at a pH of 7 and temperature of 76 F, but one experienced keeper advises that they fare better in acidic water, and recommends sphagnum moss as a substrate.  They may reach 24 inches in length, but most top out at 12-16 inches.

Caecilians are quite shy at first, and must be provided with subdued lighting and artificial caves, PVC pipes, live plants and the like as shelter.  Those I’ve kept have become quite bold after a time, leaving their hideouts by day when scenting the earthworms, blackworms and prawn that are their favorite foods.  A few individuals learned to take frozen foods and shrimp pellets, but live food is definitely preferable.

Fish keeping experience will serve you well in caring for these fascinating amphibians…with so much still unknown about them, I hope that more aquarists take up the challenge!

Further Reading

You can read more about this and other caecilians here.

Please write in with your questions and comments. 

Thanks, until next time,

Frank Indiviglio

Tylphlonectes natans image referenced from wikipedia and originally posted by Christophe cagé

Hello, Frank Indiviglio here.  It takes some doing to stand out among the catfishes, a group that contains some of the most bizarre creatures on earth.  Yet the Electric Catfish (Malapterurus electricus) does this quite admirably.  Indeed, this species is so unique that it and the small mouth electric catfish (M. macrostoma) are alone classified in the family Malapteruridae.

Characteristics and Cautions

The Electric Catfish has a number of qualities that would seem to mitigate against its popularity, but catfish enthusiasts, myself included, seem drawn to “unlovable” beasts.  It is no beauty, and is impossible to house with any species other than its own – tank mates that are not shocked to death are eaten!  Fortunately, it is immune to its own unique defense system.

In all seriousness, however, this fish is not for beginners.  It may reach 3 feet in length, and when disturbed emits electrical charges that are, at 400 volts, strong enough to stun adults (the strength of its charges increases with size, but even a 3 inch specimen can make itself felt).  Obviously, it is imperative that children and mentally challenged persons be kept away from electric catfishes.

Natural History

The Electric Catfish inhabits slower-moving portions of the Nile, Niger and other river systems in Central and West Africa.  The small mouth Electric Catfish is confined to the Congo River Basin and rarely appears in the pet trade. 

This species captures its prey, mainly other fishes, by releasing short bursts of electricity.  Electrical impulses are also used for defense, but do not assist in navigation (as is the case for the knife fishes). A unique pectoral muscle that surrounds most of the body generates the electrical discharges.

Pairs form during the breeding season, and the eggs are laid in a self dug or confiscated hole below a sunken log or rock. Little else is known of its reproductive behavior.

Captive Care

Despite, or perhaps because of, their formidable defenses, electric catfishes make most responsive pets. Owners invariably describe them as alert and quick to respond to one’s presence (in such cases, feed but don’t “pet” them!).  They soon abandon their nocturnal ways where food is involved.

Plan for a large, well-covered tank, as these stout fishes may reach 35 inches in length.  They seem to be fish specialists, but will also take all manner of other meaty foods, carnivore pellets, prawn, earthworms, insects, crayfishes and just about any other small animal.  Long term captives rarely discharge electricity during routine tank maintenance, but they should none-the-less be treated with respect and caution.

Captives do best under low light and in moderately soft water at 76-78 F and 6.5-7.5 in pH.  A suitably powerful filtration system is essential, as are regular water changes.  Electric catfishes prefer sluggish waters in the wild, and do not abide strong currents in captivity.  Albinos are sometimes available.

Research Potential

The Electric Catfish is yet another relatively common, hardy fish about which we know very little.  Documenting their breeding behavior would be a most interesting and useful endeavor…please consider it if your resources allow.

A New Exhibit

I recently obtained a nice group of Electric Catfishes and helped set up an exhibit for them in the new African Underwater Adventure display at the Maritime Aquariumin Norwalk, Ct.  Please visit if you have a chance.

Further Reading

You can read more about the Electric Catfish at Fishbase.

Please write in with your questions and comments. 

Thanks, until next time,

 Frank Indiviglio

Living in the Edge is actually more like it, with Hagen’s new aquarium the Fluval Edge.  Unlike many of the other new nano or desktop aquariums that have come out in the last few years, the Edge is something different.  Difficult to describe, and easy on the eyes, this cool little 6 gallon aquarium gives the small aquarium a twist in design.

The tank is made of glass, and is filtered by Hagen’s proven Aquaclear filter technology.  The unique design of the aquarium has it “hanging”out in space around its base and top.  The top conceals an access opening for cleaning, feeding, and filter access.  It looks like it jumped out of a sketch book of Frank Lloyd Wright designs.  The Edge comes in 3 colors so that you can fit it in with whatever your décor or taste may be.  Check it out, I think you will find it really interesting.

We couldn’t resist setting one of these little wonders up on display, if you visit the store find the display on the info desk on the sales floor.

Thanks, Until the next blog,

Dave

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.