A large, aggressive species, such as a queen triggerfish, is sometimes best kept singlyA diverse community of marine fishes presents quite a visual feast, especially when housed in a reef system brimming with colorful corals. However, in some stocking situations, it’s preferable to avoid the “typical” marine community (if there is such a thing) in favor of a single-species or even a single-specimen tank. Ah, but if you limit your livestock to a single species or specimen, won’t that make for a real yawner of a tank? On the contrary, sometimes systems that put the focus exclusively or primarily on a particular species or individual are among the most fascinating to observe.Here are five circumstances that warrant going single-species or single-specimen: 1. The shy, specialized feeder Seahorses, which are slow, awkward swimmers, shy by nature, and very specialized, methodical feeders, come to mind here. In your average community aquarium, these fish would basically be doomed, as they’d be unable to compete with bolder, faster-moving tankmates for food and would be unable to tolerate the brisk water movement typical of such systems. Not to mention, a community tank of any appreciable size would make it extremely difficult to provide the steady supply and high concentration of suitable food items necessary to sustain seahorses. On the other hand, in a small dedicated system with very gentle current, no competition for food, and suitable “hitching posts” to cling to, a group of seahorses can make for a truly mesmerizing display
Sometimes external stressors can cause aggression amongst tankmatesFish wounds and injuries can result from a variety of different influences, with tankmate aggression being among the more commonplace. Unfortunately, hobbyists don’t always recognize this problem right away when it manifests itself. Jay Hemdal, Curator of Fishes and Invertebrates for the Toledo Zoo, explains why in the following excerpt from his book The Salt Smart Guide to Preventing, Diagnosing, and Treating Diseases of Marine Fishes: Tankmate aggression This is a potential issue in any marine aquarium that houses more than one fish. In the most serious instances, where the aquarist severely underestimates the ability of one fish to injure another, aggression actually takes the form of predation. There are also cases of fish living peacefully side by side for years and suddenly beginning to fight. Home aquarists are often in denial that any aggression is taking place because, with the exception of the most severe cases, it is very difficult to “catch them in the act.” Take, for example, a case of minor aggression where one fish is “tagging” another one (damaging a fin with a bite) at a rate of once or twice a day. What are the chances that an aquarist is going to see the aggressive act?
Undulate triggerfish (Balistapus undulatus) are well-known for their belligerent natureLFS staffer to customer eyeing sohal tang as potential purchase: “Hmm, I don’t think that fish would be a good choice for your tank. It can get very aggressive, and most of the fish you have in there now are pretty shy and passive. Customer to staffer: “Yeah, I know sohals have a reputation for aggressiveness, but it’ll be the last fish introduced to the tank. Besides, you have to remember that individuals of a species are going to vary to some degree in their behavior. I’m willing to take my chances.”This is one of those circumstances (albeit a totally fabricated one) in which a hobbyist willingly ignores good advice and overrides common sense because, come hell or high water, he or she just really wants a particular specimen. And, in this context, referencing the variable behavior among individuals within a species is merely another manifestation of self-delusion. Don’t get me wrong, there most definitely can be considerable behavioral variation within a species. For example, I’ve kept several yellow tangs over the years, and these individuals have ranged in their level of assertiveness toward perceived competitors anywhere from pushover to outright bully