That Fish Blog – Aquarium Advice and Information

Hello, Frank Indiviglio here.  Marine, grindal, micro, white, blood and other worms drive even the most peaceful aquarium fishes wild, and with good reason – they figure prominently in diets worldwide, and are packed with important nutrients.  Research in which I was involved (Bronx Zoo) has shown that earthworms form a near-perfect diet for many amphibians, and may likely be so for certain fishes as well. 

Blackworms are a pet trade staple…today I’d like to mention a few lesser-known types.

Marine Worms, Families Neridae and Annelidae

Sandworms, bloodworms and other large marine species are seasonally available at bait stores or, where legal, may be collected under rocks along bays and tidal streams.  They are an expensive but important component of the diets of a great many saltwater fishes and invertebrates.

Several species have sharp mouthparts and can deliver a painful bite, and may be dangerous to aquarium pets as well….in fact, the hard jaw material of one sandworm is being put to industrial uses.  It is usually prudent to remove the head before feeding. 

Marine worms store well packed in seaweed under refrigeration.  They are interesting aquarium animals in their own right – please look for a future article on their care.

Microworms, Anguillula silasiae and Grindalworms, Enchytraeus bucholizi

Grindalworms are related to earthworms; microworms are not true worms, but rather nematodes. 

Both breed well in damp peat moss at 75 F, and feed upon vegetable-based tropical fish flakes.

Whiteworms, Enchytraeus albidus

Closely related to grindalworms, whiteworms fare better at cooler temperatures (50-58 F) and may be fed oatmeal and staple diet fish flakes.  Cultures are commercially available.

Bloodworms, Chironomus spp.

Unlike marine bloodworms, Chironomus are the aquatic larvae of tiny flying insects known as midges (“gnats”).  Interestingly, they utilize a form of hemoglobin to transport oxygen in the blood, much as we do.

Bloodworms are impractical to breed but are available at pet stores, and survive well under refrigeration.  Like other freshwater invertebrates, bloodworms may be fed to marine creatures, but they spoil rapidly in salt water.

Further Reading

Earthworms are the most useful of all invertebrates…a breeding colony will supply the needs of fishes and invertebrates of all sizes.  Please see my article Rearing and Using Earthworms for further information.

For an interesting article on sandworm behavior and breeding habits, please see this article.

Please write in with your questions and comments. 

Thanks, until next time,

 Frank Indiviglio.

Hello, Frank Indiviglio here. There was a time when all serious aquarists maintained live cultures of Daphnia. This practice has fallen out of favor today, with live foods being replaced by prepared diets. However, many tiny aquatic Crustaceans are easy (and interesting!) to maintain, and represent one of the most nutritious of all food sources for aquatic animals.

The animals highlighted here are especially valuable for fry and small or filter-feeding invertebrates, and are essential to the survival of tiny live food specialists such as seahorses and pipefishes. They can be used for freshwater or marine animals. Be aware, however, that freshwater species will expire rapidly in salt water, and vice-versa.

Daphnia

These tiny Crustaceans may easily be collected via plankton net (available at biological supply houses) from nearly any body of fresh water. Alternatively, a culture may set up by adding pond water and grass or hay to a tank placed in a sunny location (or use a full spectrum bulb).

Eggs or immature Daphnia magna, a very common species, will likely be present and, at 75-80 F, will mature within a week. This species reaches 0.25 inches in length (a Daphnia giant!) and is sometimes available commercially. Females produce 100 or more eggs every few days (with or without males), and so a healthy colony will easily meet the needs of most aquarists.

Daphnia fare best in tanks supporting a healthy growth of algae. While filtration is not essential, I’ve found a sponge filter
to be very beneficial (use a small air pump – strong currents should be avoided).

Decaying plant matter provides sufficient food, but growth and reproduction will be hastened if you supplement the culture with Artemia food , ground Spirulina discs and liquid invertebrate foods.

Copepods

Smaller even than most Daphnia, Copepods are an excellent food source for the tiniest of fish fry, shrimps and filter-feeding invertebrates. I’ve used them for dwarf seahorses and newborn four-spine sticklebacks with great results.

Occurring in fresh and marine waters worldwide, over 5,000 species of these crustaceans have been described to date (Copepod taxonomists must be quite amazing people!). Cyclops fuscus, which reaches 0.124 inches in length, is the species most commonly encountered in the USA.

Copepods may be collected and raised as described for Daphnia.

Seed Shrimp or Ostracods

These aptly-named Crustaceans (Class Ostracoda) do indeed resemble tiny shrimps encased within a seed. The 13,000+ described species thrive in a nearly every aquatic habitat known, from the deepest oceans to the few drops of rainwater that collects in bromeliads growing in rainforest canopies. They are truly amazing in their range of forms and adaptations.

Seed shrimps “bounce” along the substrate, a habit that renders them an ideal food for bottom-dwelling aquarium pets. Although rarely cultured for food, I have found them to be quite hardy, and well worth the small effort involved in keeping them. Their exoskeleton is an excellent source of calcium.

Seed shrimp care is as described for Daphnia.

Useful Products

A number of highly nutritious crustacean-based foods are available to supplement live-food diets. The following are well-worth trying:

• Zooplankton Diet
• Liquid Invertebrate Foods
• Freeze-dried/Frozen Daphnia

Further Reading

Despite their small size, seed shrimps are incredibly complicated creatures, and quite interesting in their own right. Read more about their structure and behavior at http://w3.gre.ac.uk/schools/nri/earth/ostracod/introduction.htm.

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

Copepod image referenced from Wikipedia and originally posted by Uwe Kils

Hello, Frank Indiviglio here.  In terms of species diversity, fishes are the most successful of all vertebrates…with over 25,000 species identified so far, they outnumber mammals, reptiles, amphibians and birds combined.  Ranging in size from 2/5 of an inch to over 40 feet in length, one fish or another has colonized every aquatic habitat imaginable, from desert pools of 104 F in temperature to frigid Antarctic seas.  

In keeping with this remarkable diversity, fish reproductive methods are also extremely varied.  Today I’d like to convey some interesting facts concerning the breeding habits of both aquarium and non-pet trade species.

Placing the Young out of Harm’s Way

All American and European eels, whether inhabiting a bay in New Jersey or a pond in England, originated as eggs laid in the Sargasso Sea, off Bermuda.  Eels, salmon and many other fishes engage in massive breeding migrations, with millions of adults laying eggs simultaneously and then dying shortly thereafter. 

Most fishes lay eggs (up to 35 million per season in some cases), but a great many are live bearers that reproduce via internal fertilization.  Many merely scatter the eggs or fry and leave them to take their chances, while others take great precautions in preparing nests, guarding the eggs and caring for the young. 

Adult tilapia and many others protect their young by taking them into their capacious mouths at the slightest hint of danger, while male bullhead catfish accompany their offspring on feeding forays for several weeks (please note the photo of a brooding Cyphotilapia frontosa – youngsters can be seen within the parent’s mouth).  Perhaps most surprising of all, discus fish produce unique skin secretions that serve as food for their fry.

Switching Sexes and Sex Roles

Many fishes depart radically from what we’ve come to know as “typical” vertebrate reproduction.  Female seahorses, for example, deposit their eggs in the pouches of the males.  The males then act as “surrogate mothers” – regulating the salinity of the water in the pouch, brooding the eggs, and bringing forth the young. 

Wrasses, many species of which are kept by marine aquarists, begin life as females, with a number becoming males at a later point, a phenomenon known as protogyny. 

The ever-popular clownfishes utilize an equally unusual reproductive strategy, known as protandry.   All clownfishes fishes start out as males, and some later change their sex and wind up as females. 

Cloning (with a twist)

The Amazon Molly (Poecilia formosa) adds yet another variable to its reproductive strategy.  Named for the female-only Amazon Tribe of Greek Mythology (it ranges from southern Texas to northern Mexico, and is not found in the Amazon River), only females are known.  They must, however mate with a male to stimulate egg development – but there are no male Amazon Mollies. 

Female Amazon Mollies solve this dilemma by mating with males from one of several related species that share their habitat.  None of the “father’s” genetic material makes it into the young mollies however – these are all clones of their mother!

Well, we could go on for pages…I’ll add other interesting tidbits in the future.  Until then, please write in with your own odd facts and any questions you may have. 

Further Reading

To learn why inbreeding has not doomed the Amazon Molly to extinction, please see this article.

To read more about seahorse reproduction, please see my article The Care and Natural History of Native Seahorses.

Thanks, until next time,

Frank Indiviglio

Mouthbrood image referenced from wikipedia and originally posted by MidgleyDJ photo by Matthew Miller

Hello, Frank Indiviglio here.  Please see Part 1 and Part 2 of this article for general information on Damselfishes and their close cousins, the Clownfishes, and for notes on the care of the beautifully-colored Percula clownfish, Amphiprion percula.

Damselfishes in the Aquarium

Damselfishes are generally small, brilliantly-colored and in near constant motion.  These characteristics, along with their general hardiness, render them quite popular with aquarists.

Despite their small size, most damselfishes survive quite well in aquariums with larger fishes.  However, most are very territorial and rather aggressive towards their own and similar species (please see below).

Taxonomy

Together with the ever-popular clownfishes, the damselfishes are classified in the Family Pomacentridae, which contains over 325 species.  Many are superficially similar in appearance but differ greatly in habitat choice, food preferences and other regards, and ichthyologists (fish scientists) describe new species regularly.

Marine Gardeners

Damselfishes seem inordinately protective of their territories, so much so that these tiny warriors will even attempt to drive off human divers!  Research has revealed that several species engage in “aquatic farming, with mated pairs protecting beds of algae, a favored food.  Thick mats of algae often grow within well guarded territories but are absent outside these territories, due to a large number of other fishes and invertebrates that feed upon algae. 

The industrious little damselfishes have even been seen to “weed” their algae beds by removing debris and, possibly, competing algae species.

Further Reading

An interesting article on the relationship between Cocoa Damselfishes, human activities, coral reef health and algae is posted here.

I’ll discuss the care of various damselfish species in future articles. Until then, please write in with your questions and comments. 

Thanks, until next time,

 Frank Indiviglio

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