I know everyone will be shocked by me challenging conventional wisdom but I see and hear advice on shoaling fish pretty often that goes something like the following. "That is a shoaling fish. It shouldn't be alone, you need at least x of them." Where x is typically either 5 or 6. Sometimes the word "school" is used instead but I don't believe that there are any freshwater schooling species. Although, I could be mistaken there.
After keeping quite a few shoaling species over the years, mostly tetras, my opinion has become that those numbers are way too low. I don't know exactly what the right number is but I think it is more in the 20+ range than the 5+ range. I have commonly kept groups of tetras in groups of 8-12 individuals and the only time I typically witness anything like shoaling behavior is when the fish are stressed or frightened. On the other hand, put a group of 30 tetras, especially in a larger tank and they demonstrate that behavior nearly all the time. I am not sure where those numbers came from but I suspect it is based more on the number of the same fish that people were willing to put in their tank then anything else.
Now, there are fish, especially some of the more gregarious cichlids that seem to do fine in smaller groups. I am not sure that these are really "shoaling fish" though. If they are they are the shoaling behavior is clearly different than that of Characins and Corydoras species as examples.
Just to be clear on what I mean here, the two times I have kept large shoals of tetras, they have kept together nearly all the time. In fact, the only time they didn't was at feeding time when the food was on the bottom of the tank. In smaller groups the behavior is different. Sometimes they will pull together but they would not always be that way.
Clearly, my sample size of 2 larger shoals is not conclusive. I would be interested in hearing others opinions on this, especially those who have kept large groups of shoaling species.
After keeping quite a few shoaling species over the years, mostly tetras, my opinion has become that those numbers are way too low. I don't know exactly what the right number is but I think it is more in the 20+ range than the 5+ range. I have commonly kept groups of tetras in groups of 8-12 individuals and the only time I typically witness anything like shoaling behavior is when the fish are stressed or frightened. On the other hand, put a group of 30 tetras, especially in a larger tank and they demonstrate that behavior nearly all the time. I am not sure where those numbers came from but I suspect it is based more on the number of the same fish that people were willing to put in their tank then anything else.
Now, there are fish, especially some of the more gregarious cichlids that seem to do fine in smaller groups. I am not sure that these are really "shoaling fish" though. If they are they are the shoaling behavior is clearly different than that of Characins and Corydoras species as examples.
Just to be clear on what I mean here, the two times I have kept large shoals of tetras, they have kept together nearly all the time. In fact, the only time they didn't was at feeding time when the food was on the bottom of the tank. In smaller groups the behavior is different. Sometimes they will pull together but they would not always be that way.
Clearly, my sample size of 2 larger shoals is not conclusive. I would be interested in hearing others opinions on this, especially those who have kept large groups of shoaling species.
