Can we talk about 6?

[Pepere]

Why 6?  It is common knowledge that shoaling species should be kept in groups of 6 or more,  but how was that number arrived at?  What is the science behind it? Was there actually science behind it?

 

why not 5?  Why wasnt the magic number determined to be 7?

 

do you see significant behavior changes if you have 6 and then 1 dies?  All of a sudden the fish say my goodness there are only 5 of us now….  We dont know what to do…

 

 

Edited September 23, 2022 by Pepere

[Cinnebuns]

I don't think it's a black and white thing at all. Ideally most species probably want to be in the hundreds but we know that's not possible. But I also think there are more factors in a school or shoal doing well than just numbers. Numbers just increases your chances of success. Other factors include:  Male to female ratio, tank size, hiding places, line of sight, etc.  All of these can arguably make a group less than 6 work depending on various factors. 

Now, why was 6 chosen?  Idk. Maybe it's a nice round number for our heads to use. Tbh, this might be a large factor. Idk if one would see significant behavior changes at 5 or not but I suspect not for most species. 4 you might start to tho. Purely generalizing and guessing here tho. 

[Pepere]

In my main display tank I started with 6Green Neon Tetras…. I then bought more and added another 6.

It is awfully nice to watch them go from a  full school to watch them break off in to groups to go in different directions and then come back together again…

when I first got my Emerald Green Cories I bought all 5 the store had in stock.  2 died with a water change and I have been struggling to get replacements through quarantine.  I have had 5 from local petco die in quarantine… I have 2 remaining that seem to be doing ok,  these are from new shipment to store, every cory from the first batch they had eventually died…...I have been trying to get their number up to 6….

 

I am getting a shipment of American Flag fish next week to go in quarantine and will try buying yet another Emerald Green Cory to try to get through quarantine….

Edited September 23, 2022 by Pepere

[Janoš Bećar Pecaroš]

Mathematically speaking, number 6 is the smallest perfect number, which means that if proper divisors of 6 are added up, sum equals to 6. 6 can be devised by 1, 2, and 3. 1+2+3=6

[Pepere]

On 9/23/2022 at 7:46 AM, Ištvan Bećar Pecaroš said:

Mathematically speaking, number 6 is the smallest perfect number

Well, I have passed 57 years on this planet before being exposed to the concept of perfect numbers….

 

 

[Janoš Bećar Pecaroš]

On 9/23/2022 at 6:54 AM, Pepere said:

Well, I have passed 57 years on this planet before being exposed to the concept of perfect numbers….

 

 

There you go, you learned something today. And day without learning is like a day without sunshine. 

[Pepere]

On 9/23/2022 at 8:23 AM, Ištvan Bećar Pecaroš said:

There you go, you learned something today.

Not a day goes by I dont learn new things.

 

the challenge at 57 is to have the learning outpace the forgetting…

[TOtrees]

On 9/23/2022 at 6:15 AM, Pepere said:

Why 6?  T is common knowledge that shoaling species should be kept in groups of 6 or more,  but how was that number arrived at?  What is the science behind it? Was there actually science behind it?

why not 5?  Why wasnt the magic number determined to be 7?

I feel like this is a lead-up to “is it okay to have 2 [insert species here]?” or “I have 2 [insert species] and the internet says I should have at least six, so clearly the internet is wrong because the two that I have are doing just fine”. 

On 9/23/2022 at 7:24 AM, Pepere said:

I have 2 remaining that seem to be doing ok,  these are from new shipment to store, every cory from the first batch they had eventually died…...I have been trying to get their number up to 6…

There it is 🤣

Just kidding. My advice is you do you. OK, that’s a too cavalier, here’s what I’m trying to say… if those two fish are doing fine and not causing problems for any others (I’m thinking of neons or tigers that become terrible fin nippers in low numbers), then getting more isn’t really a priority. I agree with what you wrote above about getting lots more than six, and see the benefits of that. I did the same with kuhli loaches and fork tail rainbows and I agree, the best number is as many as you can get.

As to your original question, why not 4, 5 or 7, maybe the answer lies in selling tactics. Six for $20 or buy 5 get 1 free, is likely to yield higher sales than a straight unit price. But that doesn’t take away from the reality that more is better (for the fish).

Ps i’m in the same situation as you with harlequin rasboras. I have 2 in my community tank, that are the survivors survivors from the original half dozen. They’re doing fine, I have no plans of getting any more. I keep my eyes open for anyone looking to add a couple to their school but I’m not actively looking to move them. 

[Pepere]

On 9/23/2022 at 8:43 AM, TOtrees said:

I feel like this is a lead-up to “is it okay to have 2 [insert species here]?”

No.  I have no interest in only keeping 2.  I was seriously wondering if there were studies showing 6 to be an optimum minimum.  I do keep my eyes open for additional black kuhli loaches too…

And I also have plans to add a 75 gallon tank in another year….

When I restarted I got a 29 gallon as it was the biggest I could fit in a particular spot in my bedroom. I only had experience with 10 gallons before. The 29 seemed huge in comparison.  It seems to have shrunk somewhat…

Edited September 23, 2022 by Pepere

[Janoš Bećar Pecaroš]

On 9/23/2022 at 7:50 AM, Pepere said:

No.  I have no interest in only keeping 2.  I was seriously wondering if there were studies showing 6 to be an optimum minimum.  I do keep my eyes open for additional black kuhli loaches too…

And I also have plans to add a 75 gallon tank in another year….

When I restarted I got a 29 gallon as it was the biggest I could fit in a particular spot in my bedroom. I only had experience with 10 gallons before. The 29 seemed huge in comparison.  It seems to have shrunk somewhat…

I believe that’s a common problem with fish tanks, they all get smaller over time.

[gardenman]

I watch a lot of fish store tours and ten seems to be the magic number in many overseas shops where fish are sold in multiples of ten. I think our retailers think people are more inclined to buy six than ten, so they recommend keeping six of them. I've kept largish schools of fish and had all but one eventually die off and the one left seems fine, so I'm not sure it's a huge issue. As long as no one's trying to eat the one that's left and he's still getting fed, just one seems pretty darn happy on their own. 

[Bev C]

In my main tank  i have a older  grandparents age community mixed  tank  of tetras and cories and i am letting my tank thin out    i am not getting any new fish unless they are bottom dwellers 

and right now i have odd number of different tetra but they have been together for so long they just hang and adopt each other   yes i know they are happier in a school but i have a happy tank,, 

When i buy fish my LFS  usually sells 6 for a large school  and 3 for a small school. They usually pair  2 males to one female 

Edited September 23, 2022 by Bev C

[Wrencher_Scott]

When it comes to bullying I could plainly see a difference in 5 to 6 discus. What I mean is when you have a bully that last one of six really seams to make a difference. It looked to me like he was just getting tired of chasing so many. I did have a bully so bad I finally traded it off though, I don't think having 10 would have mattered and 10 is too many for me anyway.

There are so many variables though, but I think 6 is a good number to pick if you must pick one.  But looking on the internet for anything is a crap shoot anyway. 😆

Fish are funny creatures, every one of them seem so different. 

Also, isn't it usually said that with schooling fish the more the better? In the wild I'm sure more than 6 would be preferred with most fish. So 6 is considered a minimum. 

Edited September 23, 2022 by Wrencher_Scott

[Wrencher_Scott]

On 9/23/2022 at 5:50 AM, Pepere said:

No.  I have no interest in only keeping 2.  I was seriously wondering if there were studies showing 6 to be an optimum minimum.  I do keep my eyes open for additional black kuhli loaches too…

And I also have plans to add a 75 gallon tank in another year….

When I restarted I got a 29 gallon as it was the biggest I could fit in a particular spot in my bedroom. I only had experience with 10 gallons before. The 29 seemed huge in comparison.  It seems to have shrunk somewhat…

How much time do you have? Like to read A LOT?  lol

I skimmed through this and it's interesting but way too much for me to ingest.

https://www.researchgate.net/profile/A-Kasumyan/publication/264977013_Patterns_and_mechanisms_of_schooling_behavior_in_fish_A_review/links/579f32b008ae802facbe8e2c/Patterns-and-mechanisms-of-schooling-behavior-in-fish-A-review.pdf

[lefty o]

i dont know, but i like 13. seems all those small schooling fish are even happier when in numbers greater than 10. also while they may not be happiest, i have had them do just fine all by themselves.

[redfish]

One is none and two is one.  Sooo, 6 is really only 3. 🤷‍♂️

[Odd Duck]

I will read the article, just not tonight because I’m coming off a long shift and have tired brain.

IME, most fish only seem to be able to count to about 4 or 5.  If you start with a group of 3 sassy fish, somebody always gets picked on by the other 2.  Group of 4, somebody will often get picked on.  Group of 5, less likely somebody gets picked on exclusively.  Group of 6 or more, any aggression tends to get dispersed across the group and usually no one gets picked on excessively.  This doesn’t hold true for every species (I’m looking at you, pea puffers).

There certainly are exceptions, but it’s a half decent rule of thumb to start with.  It’s fairly obvious to anybody that has kept larger groups that peaceful fish are more comfortable in larger groups but every group’s magic number is different for when they hit their species’ tipping point into more open, bolder, more confident behavior.  There’s safety in numbers for the peaceful species.

As far as a fin-nipping type group thinning or dwindling down, it doesn’t seem to have the same effect as a group that’s starting up.  The fish have already settled into their pecking order and they already know “Bob” is harmless enough.  Bob knows his place in life, so there’s no point in picking on him.  Peaceful groups that have already settled in comfortably may or may not change their behavior as a group dwindles if they are still comfortable in their space.

[Ken Burke]

Lots of good thoughts here!  
 

@lefty o has a really good point, schooling/shoaling fish do best with larger numbers.  I also feel like larger tanks make them happier.  I had several cardinal tetras in a 20 gal tall, when I moved them to my 75 gal and added a few to the school, wow.  
 

Each species is unique, so 6 tetras is not the same as 6 tiger barbs or 6 angels.  Having adult 3 angels (1 female, 2 males) worked well when one of the boys was smaller, but when he caught up I had to separate them. But the 3 glowlight tetras I have in my 75, pal around near the cardinals with no problems.  
 

Since the genesis of your question is about cories: you’re fine with 3 or 4 in the tank.  I started with 3 panda cories.  They were happy enough to spawn, now (a few years later) I have a couple dozen, but have sold a couple hundred to keep their numbers in check.  you have a 75% chance that you have at least one male and one female. And a 37.5% chance that you have one female with two males.  Depending on tank conditions, there’s a good chance they will spawn for you and that could give you the 6 or more numbers toy are looking for….