That Fish Blog – Aquarium Advice and Information

Brandon here. One of my favorite types of fish is one that is often overlooked because it lacks the cute appearance that so many other saltwater fish brandish.  In fact, many people believe them to be one of the ugliest saltwater fish we import here at That Fish Place.  The orange toadfish and freshwater lionfish are just two of many different species that belong to an order of very odd looking fish.

All toadfish belong to the order Batrachoidiformes.  This order is home to around 80 different species of toadfish, most of which are saltwater and brackish species.  Toadfish are characterized by their scaleless bodies, extremely large mouths, powerful jaws, and drab color (with the exception of a few reef species).  They get their name from the croaking sound they produce from their swim bladder to communicate with one another and attract mates.  Caution should be taken when handling toadfish.  Many species have spines that can inflict painful wounds, and in certain species the spines are connected to venom glands.  Most species have very powerful jaws that, in a large individual, are even capable of breaking fingers!

In the aquarium, most toadfish are extremely hardy, although they are shy and tend to hide.  You can usually spot their faces poking out from under the rock work in your tank.  They can persist for extended periods of time without eating, but will gorge themselves when food is available.  Toadfish do well on a varied diet of frozen meats including shrimp, krill, squid, and fish.  Their food should be enriched with a vitamin supplement such as Vitachem to ensure that they are receiving proper nutrition.  Tank mates should be chosen carefully as toadfish will not hesitate to eat anything small enough to fit into their mouth, including each other.

Several classmates and I have been successful at breeding the Oyster Toadfish (Opsanus tau) in captivity.  In fact, they have been extremely easy to breed.  We placed seven individuals into a very large tank, fed them well, and the fish did the rest of the work.  A pair of toadfish would lay several dozen eggs on the roof and sides of a rock cave.  One of the parents would remain and stand guard.  The eggs were yellowish in color and about the size of a pea.  After about a week the eggs would hatch and the fry would stay bonded to the rock.  After a few more days the fry became free swimming and would go off in search of food.  They will not take frozen food, so live brine and ghost shrimp would be a better offering.

 While breeding the oyster toadfishes’ tropical cousins may not be as easy, they are still an interesting fish to keep in the home aquarium.  If you’re looking for a predator that is a little out of the ordinary, why not try a toadfish?

Today I’d like to introduce you to the maintenance of cold water aquariums, a fascinating but often overlooked branch of aquarium keeping focusing on marine and freshwater fishes and invertebrates from temperate regions.

Exotics Close to Home
Please don’t be misled into equating exotic and interesting creatures with “far-off, tropical places”. Shorelines, ponds, tidal pools and rivers throughout the world’s temperate regions (with the exception of extreme s. Florida, the entire USA is in the temperate zone) yield animals of unimaginable variety and interest. While it is true that many of the most spectacularly colored fishes are found in the warmer parts of the world (their bright colors likely help males and females of the same species recognize each other among the great diversity of similar species in the tropics), breeding males of many temperate fish species, i.e. the sunfishes, do rival those of their tropical counterparts.

Why keep Temperate Fishes and Invertebrates?
Animals from temperate areas offer many advantages to aquarists who live in the USA. Often, our normal seasonal rhythms of temperature and light fluctuation are sufficient to encourage such creatures to exhibit natural behaviors, and even to breed. Also, it is often easier for us to provide a wider range of foods and a more natural environment for them than we can for creatures from faraway places. In some cases, where legal, we may even be able to collect and keep native fishes and invertebrates.

Creating Natural Habitats
If you live near a body of water, try to observe firsthand the environments and habits of a variety of aquatic creatures. You might consider modeling your aquarium after a particular habitat — a tide pool, a weedy, fresh-water pond, or a river bed, for example. Take note of the local substrates, rocks and other natural items and purchase similar ones when setting up your tank prod (collecting natural substrates is risky, due to the possibility of mineral, pesticide or other chemical leaching).

Heat
Cold water aquariums are maintained in a similar fashion to tropical aquariums, but we must consider the effects of heat. Many animals from temperate regions are very sensitive to rising water temperatures and to the lower oxygen levels that accompany them. You may, therefore, need to install a chiller to moderate temperatures during the summertime.

Species to Consider
Some of the animals that I have maintained with success in cold water aquariums, and which I plan to cover in future additions to this article, include American eels, fifteen-spined sticklebacks, pygmy and other sunfishes, mantis shrimp, sea stars, Chinese sailfin suckers, weather fish, horseshoe crabs, blue claw crabs, bullheads and madtoms, white clouds, various snails, crayfish and shrimp, giant water bugs and other aquatic insects and many others.

I’ll now give a quick overview of two unusual animals – the oyster toadfish and the spider crab – which are easily maintained in unheated marine aquariums. I’ll cover their husbandry in detail in future articles.

Oyster Toadfish, Opansus tau
This unusual marine fish, ranging down the Eastern Seaboard from Maine to Cuba, seems to cross the line between fish and amphibian – its face even resembles that of a toad. In addition, toadfishes produce sounds audible above the water and certain Asian species can travel overland for considerable distances.

Oyster toadfishes will become quite tame in captivity, and, given a tank of 55 gallons or so, may well breed. Males are ferocious guardians of their eggs, and have been known to stay with nests that are exposed at low tide.

Oyster toadfishes have survived for 15 years in captivity, and will accept nearly any meat-based frozen or pelleted food as well as live shrimp, small fishes and worms. They learn to associate their owners with food, but will bite when handled, and the spines that can inflict painful wounds.

Atlantic Spider Crab, Libinia emarginata
Spider crabs, common yet fascinating if you take the time to know them, are members of a family which includes the Japanese spider crab. With legs spanning 8 feet, these giants awed me when first I observed a large group in a pubic aquarium in Osaka, Japan. American aquariums now exhibit them as well – trust me, they are well worth the trip.

The Atlantic spider crab is a valuable aquarium scavenger, and, using its tiny pointed claws to probe into nooks and crannies, misses little. Younger animals have the endearing habit of jamming algae and vegetation into the crevices of their shells, taking on the appearance of a “walking plant”. They will also nibble at this portable garden from time to time. I have found that they forgo this habit when they reach a carapace size of about 3 inches, although I have yet to discover why.

Spider crabs rarely bother tank-mates and readily consume fish flakes, pellets, blackworms, frozen food fish foods, algae and green leafy vegetables.

In the next installment of this article I’ll write about temperate, fresh water animals that are readily available in the pet trade. Until then, please write in with your questions and comments. Thanks. Until next time, Frank.

Information on the natural history of the oyster toadfish, along with a photo, is available at:
http://fishbase.mnhn.fr/Summary/SpeciesSummary.php?id=3069&lang=Portuguese