Jay Hemdal
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The Red-rimmed Batfish, Platax pinnatus
Jay Hemdal
Unfortunate experiences that people have had with this fish have taught most experienced aquarists to be very wary of this species. Large individuals, (8 to 12 inches tall) fare especially poorly. In speaking with other aquarists, it seems that there was a particular trend for juvenile specimens to live a bit better in captivity. By no means would one consider these smaller fish hardy, but there were at least some reports of moderate success.
Bolstered by this information, I acquired a juvenile that showed a spark of interest in feeding, and which lived for five months after initially having to force-feed it to get it feeding on its own (Hemdal 1985). After the subsequent death of this animal due to an apparent bacterial infection and my later entry into a career with public aquariums, I had actively avoided acquiring any further specimens. During this time, (1985 to 1995) I still heard scattered reports of success of others with this fish through personal communications, the Internet and other media. It turns out that a surprising number of these reports were cases of mistaken identity. How any aquarist could confuse the red-rimmed batfish with the duller colored, but much hardier Platax tiera I don’t know, but this happened more than a few times. The facts of a few of the other reports were highly suspect based on the information presented. In the anonymous world of the Internet, it is very easy for a person to develop dialogues with others that stray a bit from the truth. Since there is no way to check the information being presented, some people have been known to create fictitious success stories about their aquariums so that they appear to be more expert than they really are. April fool’s day is a good time to see these sorts of messages posted on the Internet.
A hobbyist once wrote an article for an aquarium club newsletter indicating good success feeding his red-rimmed batfish bananas (of all things!). This article relied on the premise that since juvenile batfish live in mangrove swamps, these fish must be adapted to feeding on fruit and other plant material. While this might apply to the round batfish, (Platax orbicularis) the red-rimmed batfish is a coral reef inhabitant; one juvenile was found in a cave at the base of a coral reef at a depth of 15 meters, (Randall & Emery 1971) quite far from any natural source of fruit as food. There were other discrepancies in the article, the author reported that his pair of fish grew to a size which was 2" taller than the height of the tank he had reported keeping them in.
Being a natural cynic, I found only a half dozen or so of these success stories that I felt comfortable believing. One batfish I saw for myself had been raised from a juvenile to the rather drab adult stage by a pet store where it had become sort of a store mascot and a testament to their fish-keeping ability.
On to the present time: despite having sworn off red-rimmed batfish for over ten years, I still found them to be very compelling creatures. I was intrigued by a recent wholesale dealer listing; "Pinnatus bat, $18 - small, 2 available - Bali. Since most of my previous experiences had been with batfish from the Philippines, I decided to try just one more of these fish in the hope that a fish from a different collection area might be sturdier. There was good reason to believe this; other species of Philippine fish are reported to be more delicate than the same species collected elsewhere. Reasons cited for this include poor handling prior to exportation, overcrowding in the shipping boxes and the collection of fish with sodium cyanide.
Upon its arrival, I was pleasantly surprised to find this fish alert and in fine shape. It began tentatively feeding on live adult brine shrimp only a few hours after acclimation. Its aquarium was kept dim with little water current and no aggressive tankmates. For the first few days, it fed slowly on adult brine shrimp that had been enriched with hydrated Dry Selco. As time went on, the little batfish became more active in its feeding and began accepting small krill (Euphasia pacifica). It showed none of the “spitting” behavior I’ve seen before where these fish attempt to eat a bit of food, then shake their head and spit it out, eventually giving up trying to feed at all.
The natural history of the red-rimmed batfish is not very well known. Apparently, juveniles are mimics of toxic turbellarian flatworms of the genus Pseudoceros or Callioplana (Randall & Emery 1971). These poisonous flatworms glide openly across the face of reef with relative impunity from predators. The red-rimmed batfish has a similar color scheme as these worms, (Gosliner, et-al 1996) but its vertical swimming motion is obviously not the same. However, this batfish showed very little shyness of people moving around outside its tank. Most easily preyed-upon, small fish are very wary of any movement outside the aquarium that might be construed as threatening. Either this fish was exceedingly dull-witted, or it had some trick up its sleeve! Wanting to test a hypothesis, I placed a net in the tank and touched it against the fish. This resulted in a surprising reaction. The batfish immediately turned itself horizontal, draped its body over a large rock and held very still. It sure looked more like a flatworm now! I removed the net from the aquarium and it took a full five minutes before the batfish began swimming normally. I tried the net ruse again. This time the batfish immediately fell prostrate to the floor of the aquarium and lay there for ten minutes. During this time, the pale gray body stripe darkened to match the jet-black color of the rest of the fish. This was enough to convince me that the batfish was indeed an active mimic of a toxic flatworm.
An interesting observation was made whenever this fish was actively feeding. It was often seen dragging its pelvic fins along the bottom of the tank as it swam slowly along. When the fins contacted a piece of krill on the bottom, the fish would rapidly rotate its head downward to where its fins had been, and snap its mouth randomly, usually capturing the food in the process. Was the fish using its pelvic fins as “feelers” for food? Would this be an adaptation for feeding in dark coral caves? Alternatively, was this just an artifact of captivity – a learned behavior?
Three years later, the batfish is feeding even more vigorously, and has grown much larger. With this growth follows the normal color change seen in this species where their jet-black body begins to develop a vertical silver-gray center stripe that eventually increases to replace all of the black color. At the same time, the long flowing fins shrink, and the bright red rim fades to orange and eventually disappears altogether. I have always been dismayed that these “prince among fishes” are destined to grow up to be “frogs”.
More recently, Bali Aquarich has been producing tank raised red-rimmed batfish in reasonable numbers and at a fair price. These do not have the aversion to food that is so often seen in wild caught specimens.
I still feel that the vast majority of wild caught red-rimmed batfish imported into the U.S. do not survive for long. There are however, things that an aquarist can look for in an attempt to better their odds at keeping these fish alive:
1) Search for the smallest specimen available, and perhaps avoid ones collected in the Philippines. Don’t forget that if you are successful, your fish will eventually grow as large as the other species of batfish and will lose all of the color and grace that attracted you to it in the first place.
2) Avoid a batfish that is “ADR” (Ain’t Doing’ Right) in any respect. Folded dorsal and anal fins are a bad sign, as is any damage to the fins themselves. These fish seem very prone to external secondary bacterial infections brought about by physical trauma.
3) See the fish eat at the store before you buy it. A healthy red-rimmed batfish will feed moderately actively, chasing after food up to 4" away. Avoid a fish that only eats food which drifts right in front of its snout, or one that attempts to feed, but then spits the food back out.
4) Red-rimmed batfish do best if kept by themselves in a tall, dimly lit aquarium with few decorations. Be prepared to offer your fish live adult brine shrimp fortified with Selco or other nutrients as a starter food. When the fish seems willing, begin adding small krill, live guppies and gelatin foods to its diet.
5) Interestingly, they are highly attracted to the red dot of a laser pointer when it is shined on the bottom of their tank. A normally quiet and slow batfish will go crazy chasing after the light, trying to snap it up. This may well have an application for getting reluctant batfish to begin feeding in captivity.
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