Aquarium Portrait - A Kingdom for a Single Fish

Front view of the 32-gallon (120-L) aquarium – full of macroalgae, hardy corals,  and enchantment, with no stress, the way an anglerfish likes it.

 By Inken Krause
Excerpt from CORAL, May/June 2010

How decadent: A whole aquarium for a single fish! Actually, not at all, as this particular fish may not be a wildly popular species, but it is a much-loved pet. One that may enchant the human observer with its bizarre charm, but has no time for tankmates – or rather has too much time for them, specifically at mealtimes! Hence the little creature has to be kept in “solitary confinement”, or in a species aquarium, as we prefer to say.

The fish in question is an Painted Frogfish (Antennarius pictus). In my aquarium he is King of all he surveys. Or rather Queen, as I think it is a female. I would like to relate the story of this fish (which would be classed as a monster in any fairytale) and in particular its glass home.

Long live the queen!

Many people find anglerfishes ugly. Not I! Admittedly not one single member of the entire family Antennariidae can be described as a classic beauty, and anatomically speaking they are little more than a mouth and gullet. They are sedate and portly creatures, with a waddling gait and warty toad-like skin. In addition they are regarded as rather tricky to keep in captivity.

Caption Right: Antennarius pictus – the fish remains motionless for hours in this resting position among the rocks and algae. But if potential prey swims by, the anglerfish springs to life lightning-fast.

That may be true for some, but my lady anglerfish is very easy to maintain. Without doubt an exceptional specimen, a little queen even. She has been living with me for more than a year now and has doubled her size during that time. The secret of her successful maintenance appears to lie in apparent neglect, as apart from the occasional feeding an frogfish values its peace and quiet – quite the phlegmatic lurking predator.

I am almost inclined to think that the numerous reports of mishaps in frogfish maintenance are nearly all the result of a single mistake: long-term over-feeding. Bizarre though this may sound, a frogfish is programmed for one thing and one thing alone on most days: eating! Anything remotely edible that swims or floats past its nose is greedily swallowed, and this reflex, essential for the survival of a slow-moving predator in the natural habitat, can lead to its downfall in the aquarium. For this reason there are no opulent banquets in the palace of the Fish Queen, but instead I feed relatively sparingly and only once or twice per week.
 
The Palace

This small, 32-gallon (120-L) aquarium was originally the home of my seahorses. After these were moved elsewhere it looked sad and empty as the only décor that remained was a few rocks and some macroalgae. For a long time my search for an occupant that was interesting but as easy as possible to maintain remained unsuccessful – until, during a visit to an aquarium store, I spotted two eyes, as alert as they were greedy, looking back at me. They belonged to the then still young A. pictus, and at that very moment the decision was made.
 
BEFORE, top, and an instant later, ABOVE: The Painted Frogfish is acclimated to dead food and feeds from its owner’s hand. Note its esca, the “fishing lure” at the tip of the "fishing rod" or illicium that projects from its forehead, used to attract live prey, but also brought into play to “attract” the dead food fish in the aquarium.

Naturally the predatory habits of the frogfish meant that all other creatures that might represent potential frogfish fodder had to be removed. In other words, everything that moved and was not appreciably larger than the anglerfish herself. But, inspired by Daniel Knop (2000) and his publications on species aquaria, I took this happily in my stride. The aquarium décor was changed, as while the seahorses had enjoyed the algae as something to which to cling, the preferred home comforts of an frogfish are exposed places in which to lurk. Hence with the aid of two pillars of reef ceramic I erected a throne for Her Majesty, as befits a royal occupant.
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Blastomussa wellsi – stony corals like this fit in well in a species aquarium with minimal equipment.
Blastomussa wellsi – many hardy stony corals like this fit in well in a species aquarium with minimal equipment.

And because just rocks, algae, and a sedentary fish are not particularly exciting (visitors in particular are prone to remarks of this kind), I found room for a number of particularly attractive corals. Although the lighting and water management in the small tank are somewhat wanting when it comes to the maintenance of very demanding cnidarians, nevertheless not only the usual soft corals but also a few carefully selected stony corals such as Acanthastrea, Blastomussa, Micromussa, and Scolymia are thriving. As a result my singleton frogfish also has a treasure to watch over – and sometimes I get the impression that she is surveying her jewels with pride – or maybe she is just thinking longingly about the next mealtime...

Sarcophyton elegans - The Fiji Yellow Leather Coral is an excellent soft coral for a predator/species aquarium with minimal equipment.

Courtiers and Subjects

As already mentioned earlier, a frogfish will regard any company as no more than its next meal. Nevertheless my specimen didn’t end up completely alone, as five recalcitrant Monaco Shrimp, Lysmata seticaudata, a Mediterranean and European Atlantic species, refused to allow themselves to be caught, and so I had to abandon them to their fate. And in fact, despite innumerable attempts, the anglerfish has proved unable to capture and eat a single one of them. The little shrimps are quite simply too nimble and too cunning, spending the day in caves and crevices and coming out only at night to look for food. At the same time they also keep the endlessly regenerating population of Aiptasia sp. in check – perhaps the frogfish even appreciates the usefulness of her little gardeners.

For a while she also enjoyed the company of a Moreton Bay Lobster (Thenus orientalis), too large and bulky for even the greediest predator. But an attempt to repeat this success with a somewhat daintier [[Spiny Lobster]], (that I thought to be suitably large), proved a fatal mistake, as it was eaten – armor, antennae, and all – and took the anglerfish a week to digest. But nevertheless, thanks to the company of the shrimps, corals, and a number of snails and hermit crabs, which apparently aren’t considered worth devouring, my lady frogfish is by no means a Queen with no subjects.

Why a Species Aquarium?

There is no doubt that an aquarium for a single fish is not everyone’s cup of tea. Especially when the fish in question has no bright colors and doesn’t swim around tirelessly, display, or otherwise attract the favor of the observer. But I hope that my enthusiasm will demonstrate that a species tank of this type is worth considering and can provide a lot of pleasure! Especially if the object is to set up an energy-saving aquarium, as discussed in CORAL's Smart Reefs Issue (March/April 2010). The minimalist equipment used in my tank (lighting, protein skimmer, current pump) uses only 41 watts of electricity in the middle of the day. In view of this extremely low energy consumption, a species tank of this type is perhaps also worth considering as a second aquarium.

To sum up: anyone who doesn’t have to have it all – lots of colorful fishes, corals in all colors and forms, and all giant-size – can almost always gain more than he or she loses. And when it comes to choosing the right fish: hoorah for ugly (and predatory)!

AQUARIUM Details

SIZE, VOLUME, TIME IN OPERATION: 28 x 13 x 20 inches (70 x 35 x 50 cm; L x W x H), 32 gallons (120 L) approx.; since December 2005.
CORALS: Acanthastrea spp., Blastomussa wellsi, Blastomussa merleti, Caulastrea furcata, Goniopora palmensis, Micromussa sp., Pseudopterogorgia bipinnata, Sarcophyton elegans, Scolymia australis, Sinularia sp., various mushroom anemones and zoanthids.
FISHES: 1 Painted Frogfish (Antennarius pictus).
NON-SESSILE INVERTEBRATES: 5 x Lysmata seticaudata, various hermit crabs and snails.
LIGHTING: 2 x 24 watt T5 (Aqua Medic Sunbeam).
WATER MOVEMENT: Tunze Nanostream 6025 (660 gallons/2,500 L per hour).
WATER MANAGEMENT: Tunze Nano DOC protein skimmer.
DECOR: Reef ceramic (Korallenwelt Rostock), small amount of living rock.
MINERALS, MAINTENANCE: Weekly partial water change, 10% approx.
FEEDING: Smelt or shrimp once or twice per week for the anglerfish; occasional flake food for the Lysmata seticaudata.
OWNER: Inken Krause, Greifswald, Germany.

References
Knop, D. 2000. Artenaquarien. KORALLE 5, 1 (5): 14–21.
– 2009. Kostenbewusste Korallenriffaquaristik. KORALLE 59, 10 (5): 26–34.

Michael, S. A PocketExpert Guide: Marine Fishes. Microcosm/TFH, 1999.

Michael, S. A PocketExpert Guide: Reef Aquarium Fishes. Microcosm/TFH, 2005.