That Fish Blog – Aquarium Advice and Information

Hello, Frank Indiviglio here.  I have always included insects in the diets of a great many fishes, including shallow-water marine species (in the accompanying photo, you can see a number of typical community aquarium species swarming around a cricket).  Please see Part I of this article for further information on the role of insects in marine and fresh water fish diets.

My Experience with Wild Fishes

Whenever I have the opportunity, I toss insects into natural water bodies.  Time after time, be I near a quiet pond in Ohio or a salt marsh on Long Island, the insects never last more than a few minutes before being consumed by resident fishes.  Eventually, I came to believe that terrestrial invertebrates play a great role in the diets of numerous freshwater, brackish and even marine fishes (many insects fly far out over the ocean, especially on migrations, or are carried there by the wind).

Current Research

Just this month (August, 2009), biologists at the National Oceanographic and Atmospheric Administration published the results of a research effort which addressed this very topic.  Surveys of fishes in lakes across North America have revealed that terrestrial insects comprise up to 100% of the diets of some fish species (my own casual observations are rarely validated in such a timely fashion!). 

However, in lakes where development has eliminated shoreline vegetation, insects typically make up only 2% of the diets of the same fish species.  The importance of insects is evidenced by the fact that fishes living in lakes with developed shorelines take in 50% less energy on a daily basis and grow slower than those in undeveloped lakes.  Fortunately, re-planting even a narrow fringe of bushes and grasses along a lake can dramatically increase terrestrial insect populations.

Canned Insects for Aquarium Fishes

Both live and canned insects are eagerly accepted by many typical (and untypical!) aquarium fishes. Canned invertebrates may be better suited for most aquarists, who, unlike their reptile-keeping colleagues, are not often in the habit of maintaining live insect colonies. What’s more, they retain all the nutrition of live insects but are far more convenient to store and use.

Canned grasshoppers and adult crickets are ideal for large carnivorous fishes such as Oscars and other Cichlids, arowanas and many catfishes, and can also be crushed or chopped for smaller species.  Other varieties of canned invertebrates include snails, mealworms, silkworms and young crickets . Freshwater shrimp , also available in cans, are eagerly taken by a wide array of fishes. 

Further Reading

In some habitats, the availability of “junk food” is reducing the role of insects in fish diets.  To learn more, please see http://www.sciencedaily.com/releases/2004/09/040928101517.htm.

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

Hello, Frank Indiviglio here.  Anyone with an outdoor swimming pool is aware of the vast numbers of insects that continually crawl into or alight upon the water.  If you now consider how many billions of terrestrial insects find their way into the world’s fresh and marine waters each day, you will quickly realize that fishes have ample opportunity to consume a food item that is not usually included in captive diets (and lets not forget about the millions of aquatic insect species).  Small wonder that earthworms, crickets and waxworms are among the most effective fishing baits known.

An Overlooked Resource

However, while the sale of live and canned insects to reptile owners has long been a booming business, aquarists have largely disregarded insects as a food source for fishes.  Even well-known insect specialists such as African butterfly fishes (please see photo), mudskippers and archer fishes are rarely provided with the invertebrate-rich diets they favor.

My Introduction to Insects as Fish Food

I first became aware of just how much fishes favored insects quite by accident.  As a youth I constantly experimented with mixed species “shoreline” type aqua-terrariums…green treefrogs living on branches above guppies, bronze frogs with pumpkinseed sunfishes and so on. 

 I noticed that crickets which fell into the water were set upon ravenously by whatever fishes happened to be nearby.  Dead, water-softened crickets elicited a feeding frenzy among even the most “peaceful” of fish species, such as guppies, Cory cats, platys and swordtails.

Using Live and Canned Insects

I soon found insects to be eagerly accepted by many typical (and untypical!) aquarium fishes, including freshwater, marine and brackish species.  I continue to use substantial numbers of insects as food for a wide variety of fishes, and believe that the vigor, color and health of many has benefitted as a result.  Increased feedings of insects and similar foods may also be useful in bringing certain freshwater species into breeding condition.

  Canned invertebrates offer a convenient method of providing your fishes with valuable dietary variety.  Next time we’ll take a look at their role in fish–keeping and some other examples of insect-feeding among wild fishes.  Until then, please write in with your questions and comments.  Thanks, until next time, Frank Indiviglio.

Further Reading

The archer fish feeds almost entirely upon terrestrial insects, knocking them from vegetation with well-aimed jets of water.  By specializing so, it is able to exploit a unique food source in a habitat teeming with competing species.  The Friends of the National Zoo has posted information on their care in the zoo and natural history at http://nationalzoo.si.edu/Animals/ThinkTank/Animals/ArcherFish/default.cfm.

 
Please see also the following article on our blog – Archerfish: Aquatic snipers for husbandry advice.

Image refereneced from Wikipedia and originally posted by Toniher.