There seems to be quite a bit a discussion on schooling and the proper number that schooling fish should be kept in. I thought I would try and address some of the questions members have about these subjects.
First, let us start off with the basics.
What is schooling? Schooling is a behavior in which fish of the same species gather together in large groups. These groups can number from a few individuals to thousands.
Why do some fish school? Fish use schooling for several things. First, it is a defense mechanism in which member fish of the school will bunch together in a tight ball or swarm in order to avoid predators. The school offers protection to its members by confusing predators with a type of camouflage created by hundreds or even thousands of fish with the same color pattern merging into almost a single teeming mass of light and vibration. This denies the potential predator the advantage of honing in on and singling out a particular fish. Second, schooling in a large group of the same species increases the probability of finding a mate thereby increasing the chance of a spawn and the health of the population. Third, much like geese flying in a “V” across the sky schooling offers a hydrodynamic advantage by conserving energy. The front of the school cuts through the water allowing the members toward the back to rest.
Someone mentioned shoaling what does that mean and how is it different from schooling? Shoaling is very similar to schooling and is used by fish for the same reasons, the only difference is that a shoal can consist of fish from a few different species.
What types of fish school? Many species of fish school the most common kept in the aquarium include tetras, most barbs, rasboras, danios, some species of catfish, and even a couple species of cichlid.
So why does this matter in the aquarium? My fish are not in any danger of being eaten, I’m not looking to spawn them, and at most they swim two to three feet across the length of the tank. Most tetras, barbs, and minnows with a few exceptions enjoy the company of others, but rarely exhibit true schooling behavior in the aquarium. They may not school 100% or even 10% the time as we would like, but having members of the same species in the tank gives them a sense of comfort. This reduces their overall stress level and we all know that a comfortable unstressed fish means a healthier fish. Another reason many advocate the keeping of tetras, barbs, and minnows in a school is because many of these fish tend to be nippy by nature. Keeping them in schools distributes the aggression evenly and keeps them preoccupied so they don’t end up nipping the other tank inhabitants to death.
So how many fish of a species should I add to make a school? As a general guideline it’s good to shoot for around 6. More is always better, but keeping less then six isn’t going to cause them to explode or spiral into depression just try and add to the school when you can. Also be sure your tank can handle 6 of whichever kind of schooling fish you plan to get. This tends to be more of a problem with larger schooling fish like sliver dollars or piranha.
What about a shoal in the aquarium? This is really the million dollar question and is really up for debate. Schooling fish should really be kept in just that a school. And if two schools decide to shoal together good, but this is very rare and what works for one person may not work for another. The best fish to try this with would be fish with similar body shapes and similar swimming patterns.
My schooling fish don’t form a school that much, is there anything I can do? Nope, afraid not, just enjoy the fleeting moments they do and have your camera ready.
Hope this helps some feel free to post any more schooling questions or spelling/grammer errors here.