What controls the size of bn pleco ?

I'm a bit confused on bn pleco size. I know they are suppose to grow 5-6 inches but it seems that many of the odd balls (super red, lemon, ...) are a lot smaller - closer to 3 inches. I purchased a group of 4 (they sent 6) lemon blue-eye about 2 years ago. Of the 6 4 were small and 2 large. Is there something like a dwarf gene or is there some other reason (in breeding? health issues?) that results in the fishes staying small. Oddly the male and female in a 29 grew to full size but the ones in the large tanks stayed small.

 

I don’t know the answer but a quick search on other forums suggests that others have experienced similar situations, even with fish from the same brood. Seems like there could be some genetic issue that causes some individuals to stay small despite experiencing the same conditions as siblings that grow large. Interesting…

 

I presume with a great deal of confidence that the 6 lemon were from the same brood - the super red is obviously a different brood.

 

Fish produce growth inhibiting hormones so too many fish in too small a space and they will stop growing aka stunted

Plecos are quite sensitive to it iirc

 

I'm gonna go out on a limb here.... I'd wager it has more to do with the feeding/care/husbandry of the first 12-16 weeks of life than anything else. Judging from the numbers of of large eyed/small bodied fish I see for sale all the time, I'd double down on the "stunted before it ever got to you" theory

 

This was my initial thought, but after reading a bit more it seems strange that some siblings from the same brood stay small while others grow big under the same conditions. But I suppose it could be that within a brood some individuals are much more dominant than others at obtaining food.

 

Fish produce growth inhibiting hormones so too many fish in too small a space and they will stop growing aka stunted

I'm gonna go out on a limb here.... I'd wager it has more to do with the feeding/care/husbandry of the first 12-16 weeks of life than anything else. Judging from the numbers of of large eyed/small bodied fish I see for sale all the time, I'd double down on the "stunted before it ever got to you" theory

I don’t know the answer but a quick search on other forums suggests that others have experienced similar situations, even with fish from the same brood. Seems like there could be some genetic issue that causes some individuals to stay small despite experiencing the same conditions as siblings that grow large. Interesting…

All of the above.

And I add to the genetic issue: "BN pleco" Ancistrus are already a. a hybrid species due to a lot of crossing between different species of the Genus and b. the colourbreeds are overbred as any other domestic strains of fish like rams, bettas or livebearers.

And the worst: While all are legitimate answers unless we have professionals with laboratories at hand we will never know which one it is.

 

This was my initial thought, but after reading a bit more it seems strange that some siblings from the same brood stay small while others grow big under the same conditions. But I suppose it could be that within a brood some individuals are much more dominant than others at obtaining food.

That's been my experience. I try really hard to grow fry "optimally" (large tanks, lots of food, lots of clean water), and there are points where a (small) percentage of fry simply stop progressing

 

That's been my experience. I try really hard to grow fry "optimally" (large tanks, lots of food, lots of clean water), and there are points where a (small) percentage of fry simply stop progressing

In your case (and from what I know you know your business) it will likely be the tiny number of less viable specimens you will get even in the genepools with the healthiest genetics.

 

Yes, it is normal that a few fish in any brood stay small for whatever reason. It just seems with these bristlenose varieties that it is more than just a few.

 

I purchased 2 super red BNP and they grew out in my 180g.
4 years later they are both females ..and 3-4 inches aprox.
I got 6 more to get males and 1 year later started breeding the super red .
They spawned monthly almost to the day .
Most of my breedings grew in my tanks for 8-12 months before they were truly saleable to me .
In that time it was easy to see most stayed close to the same size in two groups ..
Male and female .
Females are larger by quite a bit .
If your fry are from same spawn then larger are likely female .
Plus one with Cherryshrimp420 on growth inhibiting hormones also .
Changing water as often as possible does more than just remove nutrients .
We really don't test for much of what really happens besides what everyone knows as our cycle or waters physical properties ..
My female ended around 5-6 inches and lived aprox 8-9years with me .

 

I would say it is normal to have variety in size.
Humans come in different sizes, dogs as well, and why should fish be different?
Two of my adult Neons are monsters with close to 2inches, while others of the same batch are much smaller. Same food, same size tank... just genes poke through.

 

A few comments. The ones I purchased are now owned for 18 months. I had one full size female and one full size male and both of those were removed because they were in a 29. In another 29 i had another male/female and they stayed small but after about 12 months i moved them to a 120 and the male has grown quite a bit more but the female has remained small. The other two are in a 40b and the male is slightly larger than 6 months ago but still smallish the female is small. These don't look like runts per sey. The pair in the 40B breed regularly but i suspect a lot of the frys don't make it due to predators - the pair in the 120 are not able to get the eggs to hatch (i suspect again predators). The super red i have is in a 29 and she is a little larger than the smallest lemon female but not full size (she is also very strong red - rather nice looking beast). I can't comment on the frys in the 40B - i know some are several months old (maybe 1 to 1 1/2 inches long) but i might comment in another year as to whether they get large or stay small. Not sure what i will do - in approx 10 months i will move and then i will be able to inventory and sep the pleco out.

As for water changes the 29s get 50% water change twice a week; the 120 gets 30% water change twice a week (during the summer it gets 30% and 50%); the 40B gets 1 water change a week (50%). i consider all my aquariums over stocked but the nitrate level is well controlled (below 15 in all but the 40). The 40 is least populated but has a bit of an issue with nitrate - not sure why.

Anyway I'm not sure it is hormones given the large water changes - i think they are just small - but the males seem to still be growing - the male i gave to the lfs either grew much faster or was a monster because it was at least 5 inches after a year of ownership. My guess is total age is at least 24 months possible a bit older - they were not tiny on purchase - almost 2 inches.
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As for inbreeding that is a real concern and I will probably purchase a couple of lemon after i move to swap things around a bit to prevent these siblings from further inbreeding - however I'm not sure that will help much. I sometime wonder if most domestic pleco (as well as apistogramma and rams for that matter) are already so heavily inbred that they are all related.