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Discussion Starter · #1 ·
I realize the majority of aquarium hobbyist fish are not 'true schoolers' more of a tight shoaler...but you get what I mean with what we are familiar with as schooling aquarium fish.

With that being said, I have seens tanks with fish such as Tetras that do not stay together, they just bounce around scattered around the tank within the plants. From some research it seems as if a predator makes them school together, such as Discus fish but yet I never see them chase the Tetras so how this can be considered a predator to "scare" them I do not know. Checkout this YouTube video for reference (and I would share a link but I am not allowed to apparently so search for "Planted tank Schooling Fish HD video" by Biju George). The whole predator to impose fear seems inhumane to me, certainly if they nip or chase my fish (you would think that would make a school split up and scatter).

The second idea I have been toying with, is small fish in an oversized tank, open areas if you will. Something about these huge tanks with small schooling aquarium fish (without predator) makes them school...and I do not know if this is because they feel vulnerable in such a large space or some sort of natural instinct when in larger provided areas.

I would be curious to hear the communities loose change on this subject.

Thank you
 

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Fish are schooling for many reasons: better hydrodynamics, easier mating, faster predator detection, smaller chances of catching (predator can't eat a whole school, so only some may die). The problem is, the first two doesn't matter in a fish tank. There is not enough space for fast swimming, there is no sudden current, that needs better hydrodynamics. There is not enough space to be having problems with finding pair. So the only thing we may have are predators, bigger tanks and bigger groups. With predators it's obvious they'll start schooling - the instinct works this way. With bigger tank it's harder to know if after this plant is something dangerous? Or maybe after another? There is a chance that there might be a predator and that's enough to school. With small group of fish schooling won't give any bonus, 10 fish won't get any better hydrodynamics by schooling, they won't have so much better chance to detect danger and even when swimming together there're no fish that are "in the center" safe. So more fish means more sense in schooling.
For some time I had 20 small Congo tetra, they were schooling greatly, but my tank is too small for 20 of them, now I have 12, they school only sometimes, when hungry or when ropefish start to swim around like mad ;-)
 

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With that being said, I have seens tanks with fish such as Tetras that do not stay together, they just bounce around scattered around the tank within the plants. From some research it seems as if a predator makes them school together, such as Discus fish but yet I never see them chase the Tetras so how this can be considered a predator to "scare" them I do not know.

The whole predator to impose fear seems inhumane to me, certainly if they nip or chase my fish (you would think that would make a school split up and scatter).


Thank you
When a potential predator (really any fish larger than the schooling fish) is nearby, the small schooling fish group together to appear larger to that potential predator. Its also hard for the predator to pick out any singular fish in the group as the chaos is confusing!

I think you're giving the tetras too much credit for them to possibly know if that larger fish is really a predator or not. The reality of it is, if a fish is hungry almost any species might eat any other species smaller than it. Small fish know that big fish are a potential threat and instinct takes over in an effort to protect.

I wouldn't say its inhumane to introduce a "predator" to encourage schooling. Its actually quite natural! So long as you're not allowing that predator to snack on the small guys lol.
 
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I realize the majority of aquarium hobbyist fish are not 'true schoolers' more of a tight shoaler...but you get what I mean with what we are familiar with as schooling aquarium fish.

With that being said, I have seens tanks with fish such as Tetras that do not stay together, they just bounce around scattered around the tank within the plants. From some research it seems as if a predator makes them school together, such as Discus fish but yet I never see them chase the Tetras so how this can be considered a predator to "scare" them I do not know. Checkout this YouTube video for reference (and I would share a link but I am not allowed to apparently so search for "Planted tank Schooling Fish HD video" by Biju George). The whole predator to impose fear seems inhumane to me, certainly if they nip or chase my fish (you would think that would make a school split up and scatter).

The second idea I have been toying with, is small fish in an oversized tank, open areas if you will. Something about these huge tanks with small schooling aquarium fish (without predator) makes them school...and I do not know if this is because they feel vulnerable in such a large space or some sort of natural instinct when in larger provided areas.

I would be curious to hear the communities loose change on this subject.

Thank you
Hi Teebo,

I have a 45 gallon that I allowed to become badly overgrown when I was ill for 4+ months this winter. In the tank are a reverse trio of Turquoise Rainbowfish (Melanotaenia lacustris), a old male Apistogramma cacatuoides 'Triple Red', and about 13 or so Rummy-nose Tetras (Hemigrammus rhodostomus) along with my typical cleaning crew of corydoras, otos, and SAE.

When the tank was badly overgrown the Rummy-nose tetras seldom schooled and were content to forage in the thicket of plants. Yesterday I did a major re-set of the tank removing all of the plants, re-sloping the substrate, removed all of the Ying stones (aka Seriyu Stone but it isn't), added some pieces of Mopani wood, and did some of the glass cleaning (still have more to do).

Now for the schooling part, ever since I removed all of the dense plant cover, and opened up areas of the tank where the fish are exposed, they have been schooling again...and much more tightly too! I think that fish inherently feel 'safer' in dense cover and the need to 'school' is diminished.

45 Gallon Redux; schooling Rummy-nose tetras
 

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Interesting point about hydrodynamics. I wonder if a greater current encourages schooling. Though part of this may be patience on the photographer's part, the ADA style aquariums generally seem to have pretty good schooling behavior, and they emphasize a sufficient turnover (stronger than most Americans' tanks).
 

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When the tank was badly overgrown the Rummy-nose tetras seldom schooled and were content to forage in the thicket of plants. Yesterday I did a major re-set of the tank removing all of the plants, re-sloping the substrate, removed all of the Ying stones (aka Seriyu Stone but it isn't), added some pieces of Mopani wood, and did some of the glass cleaning (still have more to do).

Now for the schooling part, ever since I removed all of the dense plant cover, and opened up areas of the tank where the fish are exposed, they have been schooling again...and much more tightly too! I think that fish inherently feel 'safer' in dense cover and the need to 'school' is diminished.
Nice to hear your observation on the fish schooling more when there is less plant coverage.

Me, going from fish only (non-planted) and venturing into heavily planted tanks, I noticed schooling behavior, and activity levels of ALL fish really (even non-schoolers/shoalers), would lessen/decrease, the more plants there were in the tank.

Now I know it seems logical that more plants would lead one to believe the more plants, the safer the fish feel and so no need to school/shoal much, but I really don't think that is entirely correct. (Still wouldn't explain the decreased activity of non-schooling/shoaling fish in my experience).

The reason I don't think it's that is because even when I would do a massive trimming or when the tank is non-planted, I could showcase that the fish in my tanks were not stressed or feeling in any danger with the lack of plant coverage.

I observe fish behavior quite a lot and I couldn't see any sign of stress or "schooling in fear of danger" behavior. Even though it seems logical that "no where to hide" (plant coverage) would create more stressed out fish or a "need" to school for safety, I could not see any sign of stress. In fact, it seems like the fish were happier. In more dense planted tanks, the fish were less active and would venture around much. With less to no plant coverage, the fish would venture all over, color up better and spawn more frequently. I tried introducing stressors such as using my hand to chase or grab at the schooling fish, but they could care less and would not dart away out of fear.

My personal thoughts/reasoning for why the fish are less active with more plants are:
1. (more "acceptable" logical reasoning, though I have doubts it's the only reason) the mere space the plants would take up, creates less room and the fish just feel less apt to swim around (I might think the plants would create more diverse areas to explore).
2. (sort of my "theory", not proven, just speculation from observation) maybe when there is just a thicket of plant mass (which might be the whole tank if it is heavily planted), it triggers some sort of psychological response in the fish's brain and puts the fish in a state of "keep a low profile for survival".

:) just felt like putting this out there again. If only I had a half decent camera, I would make a vid showing the differences in behavior/activity (kind of too late now though, since I've downsized a ton and sold off most of my fish)
 

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I have had people disagree with me on this before. But I view schooling as a defensive measure, even if it is sometimes done pre-emptively (i.e. no apparent threat). The more cover is close by the less the need for turning your brothers sisters and cousins into cover.
 

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My Neon Tetra's school.
And so do my Serpae Tetra's.

But they don't do it all the time.

So I have no clue to what would make them school.
Mine mostly do it when they are not feeding and everything is calm in the tank.
 
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My Neons are fickle, they tend to school only sporadically, and I think I agree with Seattle Aquarist, a more open tank, with less heavily planted tends to tighten the school up more. Some fish will 'Shoal', like White Clouds do when they aren't busting around, threat displaying or chasing each other.
 

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Shoaling can be a type of hivemind if you look at the school/shoal as an organism. With many catfish you see them foraging together. but when they run into another one of the school that is stationary, they stop to see why, often finding the reason the others stopped was a food source. Almost as if they are many fingers of the same hand.
 

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Discussion Starter · #11 ·
Interesting points, just to raise another. I saw a video last night of a high-current tank where the fish would swim to one side as a school, then stop and allow themselves to drift back to the other side, then all swim together back to the other side again.
 

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I think there are a few things that you need in order to see good schooling/shoaling:

You need the right species -- some just school better than others. Rummynose tetras or harlequin rasboras are both pretty good.

You need enough fish for them to feel like an actual group, not 5-6 like you'll often hear recommended, but more like 12-15 at a minimum.

You need enough space in the tank for them to have the notion "Everybody's over there! I'm isolated here!". If the whole group takes up the whole tank, you won't see much schooling.

Temporary minor threats, like somebody walking by close to the tank, tend to draw them together without putting them completely in hiding. If some larger tank mate is not an actual threat, they'll get used to them and that won't drive schooling behavior.
 

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My experience has been that if you keep adding different schooling fish species, at a certain point the aquarium dynamics become confused and each of the 'schooling' species continually get 'lost' between species groupings and it creates while a beatuiful display, not a tight school like you are seeking.
Personally I've found Silver tip tetras, embers and rummies (separately) are the naturally tightest schoolers (at my house!), not requiring any stress-factors to keep them together. But I'd keep at LEAST 20 of each and preferably more if tank size permits.

And if your tank is less than 4' long I find the school gets stressed when it hits the walls repeatedly so do recommend a 45-75g.
 

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Discussion Starter · #18 ·
Watching videos online I can agree with your advice, I see tanks with like 5 of each schooling fish and they just wander around and bump into each other. There is however one video that really grabs my attention called "Planted tank Schooling Fish HD video" please search for it. I am extremely interested in knowing the key to this aquarium's multi-schooling success. (https://youtu.be/C5IpWPvrBMo)

I only have a 15 gallon to work with, it is a very nice rimless tank but since Embers appear to stay smaller than Rummies I will be going with all Rummies. Actually here is an example I found of Embers and a Dwarf Gourami in the same size 15 gallon tank I have, I did pause and count 20 Embers. If the link is removed it was in the parenthesis to the right of this called "Dwarf Gourami and Ember Tetras in a planted tank" (https://youtu.be/kNNnVQBp94A)
 

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I think RummyNose tetra school the best... I was in a fish shop earlier today and there was about 30 of these close together schooling best I have seen. The guy in the shop said if you get these in the tank about 10 of them they will teach the others to school I.e other tetra


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They are just ordinary zebra danios with a modified colour gene. They don't school particularly tight.
Glowlight tetras school far better.
Those are GloFish (TM)

Glowlight danios are a beautiful little fish. Darn those confusing common names... Danio choprai (choprae) is their true name and from what I've observed they school about like CPD's. Kind of loose, sometimes they get in a tight formation for short intervals, but mostly loose groupings. Also wild caught specimens are likely to school tighter than their captive bred brothers and sisters.


Glowlight danio
 
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