Any tips on getting the runt of the pack to grow

[Rtc/tsn]

So in my 29g with the blind cave tetras. Over the last month I think that I’ve had them they’ve grown incredibly. Now each nearing about 1.75-2” except for one that’s still only about 1”. He’s clearly at the bottom of the pecking order but is there anything I can do to help him out.

 

[tlindsey]

He’s clearly at the bottom of the pecking order but is there anything I can do to help him out

I personally wouldn't worry about it but if you want put in a separate aquarium and see if that helps with growth. If it's a true runt as you stated it will remain the smallest of the group.

 

[MultipleTankSyndrome]

I generally agree with tlindsey. There will be a runt in just about every school of fish, just as there would be in nature. Not really avoidable and not something to be concerned over.

 

[TwoTankAmin]

I have my own theory about this. It came from my experience breeding lf bn plecos. I would get spawns of 30-40 fish which would end up in a growout tank. There were always a few that were much smaller than the rest.

My methods were the result of being sonewhat contrained in terms of space for tanks and what sizes i could use. My practice was to pull the cave and dad to a 10 gal tank and when the kids were booted i would return the cave and dad to the breeder tank, that many fry in a 10 gal. is onlt a short term solution. Wvwn loaded witrh plans and water changed regularly, it fairly rapidly become over crowded as the fish grow. By the time the biggest fish are approaching 1 inch TL it is time to begin moving them to larger quarters and also to start selling them.

it was clear that some were growing faster . most we growing at an average pace but a few were "runts." As the bigger fish were being removed to other tanks I noticed that the smaller ones began to grow faster. This made me curious as to why these fish had stayed small and then had began growing to catch up. Here is the theory I developed.

While fish do not have overly complex brain power, I do feel that individuals are not all identical in theor behavior or in how the deal with things. With growing fish there is competition for food. The most agressive fish will always get the first choice. Some fish will compete vigorously for food. But other individuals simply are not that aggressive. For whatever reason, the are unwilling, unable or afraid to fight as hard. Likely they have lost out in such encounters in their short life. The result is they lose the will to fight as a way to protect themselves. By being less aggressive they do not get beaten up. But they also do not get the best meals which keeps them smaller.

Since I normally sell the largest fish first, this also meant the most aggressive eaters were the first to go. As more of them went out, the competion eased and the small guys were able to get more to eat because they no longer deferred to their bigger brothers and sisters.

This is not the same thing as a "true" runt. These will never attain the size most or the species does. My thinking is staying small by not competing is more of a psychological form of survival strategy as opposed to something caused by a physiological trait.

As always, this is my thinking and I could be completely wrong. I am curious what others think?

 

[xenacanth9]

Looking good, I agree with most of the stuff here

 

[Deadeye]

I have my own theory about this. It came from my experience breeding lf bn plecos. I would get spawns of 30-40 fish which would end up in a growout tank. There were always a few that were much smaller than the rest.

My methods were the result of being sonewhat contrained in terms of space for tanks and what sizes i could use. My practice was to pull the cave and dad to a 10 gal tank and when the kids were booted i would return the cave and dad to the breeder tank, that many fry in a 10 gal. is onlt a short term solution. Wvwn loaded witrh plans and water changed regularly, it fairly rapidly become over crowded as the fish grow. By the time the biggest fish are approaching 1 inch TL it is time to begin moving them to larger quarters and also to start selling them.

it was clear that some were growing faster . most we growing at an average pace but a few were "runts." As the bigger fish were being removed to other tanks I noticed that the smaller ones began to grow faster. This made me curious as to why these fish had stayed small and then had began growing to catch up. Here is the theory I developed.

While fish do not have overly complex brain power, I do feel that individuals are not all identical in theor behavior or in how the deal with things. With growing fish there is competition for food. The most agressive fish will always get the first choice. Some fish will compete vigorously for food. But other individuals simply are not that aggressive. For whatever reason, the are unwilling, unable or afraid to fight as hard. Likely they have lost out in such encounters in their short life. The result is they lose the will to fight as a way to protect themselves. By being less aggressive they do not get beaten up. But they also do not get the best meals which keeps them smaller.

Since I normally sell the largest fish first, this also meant the most aggressive eaters were the first to go. As more of them went out, the competion eased and the small guys were able to get more to eat because they no longer deferred to their bigger brothers and sisters.

This is not the same thing as a "true" runt. These will never attain the size most or the species does. My thinking is staying small by not competing is more of a psychological form of survival strategy as opposed to something caused by a physiological trait.

As always, this is my thinking and I could be completely wrong. I am curious what others think?

I think you hit the nail on the head. It’s no coincidence that the dominant individual in any group happens to be the biggest and meanest one. All about who gets the food. I have noticed in my tanks that less dominant fish are the more reluctant to eat, so you are definitely on to something about it being psychological.

 

[TwoTankAmin]

Here is something that makes this a bit more interesting. I have been breeding zebra plecos since 2006. I have noticed when I keep breeding Hypancistrus plecos in groups from 6 to about 15 fish that most of the spawning is done by just 2 males. However, my zebra alpha male was the second largest not the largest male. The largest was number 2. When I posted about this I heard back from other zebra breeders who have seen the same thing in their tanks.

Now, the two fish are nor hugely different in size but it is clear that one is bigger. My thinking is that the slightly smaller fish is simply the tougher of the two. Sometimes grit beats bulk I guess.

I bever really answered the question posed by the OP. here is what I would suggest. Either move the larger fishes to another tank to reduce the competition or move the runt to a tank where it will not have to compete. This may be a bit of a challenge of it is a schooling fish. But my bet is it will still gain size pretty fast if it isn;t challenged for food.