Changing jobs recently has afforded me the opportunity to house a 55-gallon aquarium in my office at work. Since this tank was going to be the show piece of my office, I decided to fully decorate it. I siliconed a beautiful piece of driftwood, that takes up almost half the tank, to the bottom to make sure that it didn’t float and decorated the remaining space in the tank with silk plants. I was truly proud of my office conversation piece.

After letting the tank run for about a week and a half, it was time to add the fish. The timing was perfect as the society’s monthly meeting included an auction at which I bought six Thorichthys helleri. Since I didn’t have any other fish in my office tank, I didn’t have to worry about quarantining the fish.

As my aim was to create an underwater habitat with an array of fish, I had to increase the existing population. I knew that this tank was going to be a community tank setup so I had to include some tetras. I went about listing the tetras that I found most appealing to me and settled on Paracheirodon axelrodi (Cardinal Tetra), Hemigrammus bleheri (Rummy-Nose Tetra) and Hemigrammus erythrozonus (Glow Light Tetra). To me, each of these tetras has a characteristic that really stands out more than the other tetras. The Cardinal Tetra has a body length iridescent blue horizontal stripe that is mimicked below by deep red, the Rummy-Nose Tetra has its red-capped head and black and white flagged tail and the Glow Light Tetra has its striking, literally glowing, reddish orange medial horizontal bar. I set about purchasing groups of these tetras, a process that was punctuated by obtaining ten Symphysodon aequifasciatus (Discus) that were acquired during my trip to the ACA in Denver.

I had moved from a stressful job but soon found that the new job is equally stressful, just a different type of stress! I found myself spending a considerable amount of time observing my aquarium in an effort to relieve the stress. During my countless hours of observations (I hope my boss doesn’t find this out), I witnessed something about my tetras that I have always seen in past years but, due to lack of real time to study the fish, never made a hypothesis regarding their behavior.

I had groups of “schooling” tetras that nicely schooled together (one of the reasons behind the decision to purchase them) but there was always one from every school that refused to follow the rest and seemed to prefer to explore on its own. I drew a parallel to human behavior. You select any place (other than Bermuda) and you will observe that the masses of people tend to congregate (live) in one area. There are many valid reasons why people gravitate to urban cities. With the congestion of being in large groups comes a feeling of safety and security for many. When there are events, they feel more comfortable enjoying it in the company of others. This holds true because, as humans, we are social creatures. But, there is always an exception to the rule. You will always find a person who prefers to do his/her own thing and enjoys solitude. During further analysis, I questioned if this was indeed the case for the tetras (a preference for solitude) or was it a case of them being social outcasts.

When you explore a hypothesis, you have to make sure that you exhaust all possibilities. It could be that the individual fish are not social outcasts. It could be that they are exhibiting anti-social behavior. If this rationale is accepted to be true, fish would be placed at a different paradigm. Acceptance of this theory might support a sense of cognition.

We (serious aquarists) often testify to the inherent instinctual intelligence of fish when it comes to parental care, but do they have a level of cognition that we (at least I) have never taken the time to examine? Because I have a love and fascination for the fishes that I keep, I would like to think that they have an innate intelligence. Being a member of the most intelligent genus on earth, I would hate to admit that I am enthralled by a genus that has no direct intelligence, simply instinctual pre-programmed behavior as a result of their evolutionary genetic inheritance.

As I spent more and more time monitoring my fish, drawing these parallels to human behavior, it was hard to determine the reason for the solitary “choice” of my tetras that did not school. I tend to think that, like humans of different ethnicity, they find comfort or prefer to associate with the “other” groups. I wondered whether or not fish might suffer from a lack of identity. The reason this question came to mind is because, although the individual fish did not school with its own species, it is often seen amidst the other schools. You might say that the individual fish identifies more with that particular school, but further study indicates differently. Usually those individual fish are not exclusive to that school and are seen attached to other schools, but rarely their own school.

Another reason might be that fish, like humans, observe the physical deformities of the individual fish and will ostracize them from the group. It could also be that the fish can sense genetic mutations and will only associate with viable counterparts in order to preserve and/or strengthen their lineage. In just about all species, the quest for a suitable mate is an important undertaking. By schooling, the fish have time to scrutinize the others in the school to identify the strengths and weaknesses of the other fish (in the group) to determine the best potential mate. Why include a member into the group that would not be considered as a potential mate?

There can be numerous other possibilities for this anti-social behavior. The answer may take some years of study, or through over-analysis I have failed to see a very simple explanation. If there is an answer to my pontification, I would welcome the real reason for such behavior. If there is no answer to be found at this time, this behavior would be an interesting topic of study.