Tetra School dynamics

[TomK2]

I bought 10 pristella tetras months ago. They all seemed about the same size back then. Now, the school has two really huge tetras, and the rest are relatively small.

I am guessing that this is some sort of Alpha male and Alpha female school trait? two fish in the school get huge, and the rest stay small, until an alpha spot opens up later on?

 

[severum mama]

I have 7 gold pristellas, and have had them for about a year and a half. Much like your situation, one of them is way bigger and brighter yellow than the others. I don't have any hypothesis to offer here, just the similar experience.

edit: Just remembered- my green fire tetras are the same way, but I know it's a male/female thing as there is definite sexual dimorphism with that species. 2 of the males are much bigger than any others, even other males. Interesting.

 

[Hovoc]

I have a one larger neon in my group of 5

 

[Jchillin]

Same thing happened with my lamp eyes...I got 4, one died. Two are large but one is really runty looking, nowhere near as big as his siblings. Funny thing is, it did not show up in my Serpaes, all of them have remained similar in size since day 1.

 

[rich311k]

That is interesting Bill. I have one red-eye who is half the size of the rest.

 

[BrianNY]

Great observation Tom. In nature the competition for survival is feirce. Schooling fish such as tetras both attract and repel other fish through the use of secreted chemicals. It's one way of telling a fish you belong in "my" school, and another you don't. I also believe that part of this chemical survival strategy works towards assuring survival of the fittest. The fish that has the best chemistry also produces a substance which retards the growth of others of their species.
JMO.

 

[TomK2]

I seem to remember a similar school phenomenon in SW fish, either clownfish or damsels? of course, the alpha effect in that SW situation could included a sex change as well as size differences? I just hadn't heard or read about this in FW fish. In my tank, the difference is startling, the big ones are a bit more than twice the size of the smaller ones. If I hadn't bought them all at the same time I would not believe they came from the same tank and the same time, and similar ages.

I suppose in nature, the big ones get to do all the breeding, but that increased size also makes them more prone to predation? There always seems to be a risk associated with any advantage......

 

[czcz]

Does school dynamics include dominance? Do you have dominant tetras that chase the others? Are they the most colorful and/or largest? My blue tetra is dominant and the most colorful, and is in a school of 6. (3 are smaller than the rest but are recent additions. The other 3 are similar in sinze.).

 

[Rondory]

This is interesting! I bought 6 lemon tetras and I see the same thing! They were all the same size when purchased, but there is a size difference now.

 

[Friendly]

Out of my six black phantom tetras, there is one dominant male. He is the biggest of the bunch and will chase any other phantom that comes into his territory. The weird thing is, he lets my neons swim right on by and doesn't hassle them at all. It's fun to watch another male come into his territory. The fins flare up and they battle it out . Of course the big male always wins and little guy has to swim away in defeat. Besides the big male, the other phantoms are pretty much the same size. I’m not sure if I have had the phantoms long enough to confirm that only the dominant male will stay the biggest and the rest will stay smaller. I’ve only had them for about a month.

Do you think something like this could happen at a lfs as well? I’m assuming that the tetras would have to be there long enough and introduced to the tank at the same time. I wonder if it’s possible to buy a school of tetras that have already established the alpha male/female school trait at the lfs.

 

[woodsplace1]

thinking about some tetras for my 10 gallon, how many do you recommend and what kind. At this point I only have 1 dalmation molly, 1 ADF and a clown pleco...

any suggestions should be great, or should I stay with the mollies?

would love ideas or suggestions regarding how many and what kinds...thanks!

 

[BrianNY]

I think the reason the growth limitation is more apparent in home aquariums has to do with water volume. If you're only doing 25% pwcs weekly, the secreted chemicals become concentrated and stay in the tank longer. Increasing the amount of water changed will increase the growth rate in fish.

Most likely the lfs uses a central filtering system. I'd imagine that has some effect on fish chemistry. Also, even though their stock may be there for weeks at a time, people tend to buy the larger fish. So the alpha fish are removed first and end up in our tanks.

 

[exodus]

My painted tetras show the same thing. I only have 3, but two of them are about half the size of the other one. The little ones are weenies and get pushed around, but the bigger tetra even bothers all my barbs.. he appears to have a spot staked out as well.

Interesting.

 

[Lonewolfblue]

Tiger barbs are the same way. When I got 9, only 2 or 3 got real big, and the others stayed real small, and eventually didn't survive. So I bought more big ones to even things out.