Fish runts, from your breeding???

[Magnum Man]

In my case, these are Tilapia, the parents have been removed, & are in a 250 gallon tank to themselves over the summer… these have to be from the same breeding batch… they are still in an aquarium they were hatched in, not out in the grow out tanks… the picture with the biggest fish, may be the biggest, of this group, but all are of similar size… yet I have one just a little larger than a guppy… wondering if this runt, would possibly make a normal aquarium fish, or if it would slowly grow to its natural size, or is likely to die… I’m certainly not going to keep it with fish I’m raising for food, or put it any where fish are breeding in the future… last year I had one, that I got in my bought fish, to raise... this years are grade 1, last years were grade 2 ( grade 2 were supposed to be better for aquaponics set ups, with more size variance and growth rates advertised... grade 1 are supposed to be sexed, as mostly males, & are supposed to grow faster, get bigger, & grow more consistently, for better harvest in fish farming ) the runt last year, had gotten to 2-3 inches, when everyone else was 4-5 inches, & ended up getting caught, in the big ball valve at the bottom of the tanks during a water change... this year's runt looks significantly smaller... I suspect anytime something is line bred, there is likely an increase in runts or throw backs... the ones I buy are highbred blue Tilapia developed for fish farming... these, in these pictures were bred from a pair from last years bought fish...

I think I remember other members talking about tiny angel fish they had bred… just trying to learn more about "runt" issues in breeding…

 

[GaryE]

The relative size of the eyes doesn't say good news. That's a fish, that for whatever reason, looks starved. It's probably a runt because of a digestive problem.

My limited experience keeping Tilapia/Sarathrodon is that they are who they are, at any size. They are apt to be be very aggressive with other fish, no matter how much you feel sorry for one that's small. If it were able to grow (and fish grow until they die, however slowly), it could end up as a tyrant, knocking off the competition.

 

[Magnum Man]

Because these are being farmed, they are getting plenty to physically eat. Weather that one chooses to, or can’t digest ( I’ve seen it eat, or attempt to ) at each feeding, about 3 times a day… I was kind of afraid to put it in a regular mixed fish tropical tank, and my holding tanks are tied up with earth eaters right now anyway...

 

[GaryE]

I figured the feeding was good, but the fish looks starved. That says serious health issue. But it is still a nasty fish in an aquarium, if it survives.

 

[Back in the fold]

I saw the title of the thread and thought somebody wanted to know about culling . Sad fact is that’s what you have to do . There’s always runts and deformed fish in fry and there’s no getting around it . I’ve never been able to bring myself to kill any fish and that’s populated my aquariums with many runts and “Elephant Man” fish from time to time . You could eat this poor thing anyway .

 

[Uberhoust]

I experienced a large number of runts and poorly formed Angels on my last breeding. It was a breeding of children from one of my earlier breedings and I expect that the original parents were already inbred too much.

I ended up with a number of albinos and smaller than normal fish, often with fin deformities of one sort or another. My wife really liked the small albinos, and some of the other small angels so I kept them, difficult to sell them anyways. I still have most of these small angels.

My runts never grew as fast as their normal siblings and always remained smaller. I suspect that they have internal deformities as well. Gary E might be onto something about their ability to process food. In my tank right now, to keep my wife's favorite runt living I have to heavily feed the angels (quite a bit more than I would normally feed) otherwise her favorite starts to lose weight. I thought about parasites but the small fish, and the other small ones, do not have symptoms of parasites other than not growing (normal poops, strong interest in food, and no source of parasites, other than the possibility of something brought in with mosquito larva). They started small, they grew, but never like the regular sized Angels.

 

[Magnum Man]

@Uberhoust ... curious how big your dwarfs got, & how long you've had them... did most of the runts, otherwise seem heathy??? the lil Tilapia has been in that tank for a couple months, & I still drop an algae wafer ( baby tilapia food ) into the tank each time, as I have a couple of Super Red Plecos in there, to keep some of the algae off the tank, so it doesn't get too thick, for my magnetic scrapers, & the plecos particularly like the the Algae wafers... the lil Tilapia always comes to the starter pellets, with the rest of the group, which is what they are on right now...

 

[Back in the fold]

My Aplocheilus lineatus Golden Wonder Killifish have produced a considerable number of hunchbacked bent spine fish . I started out with a single pair in December 2019 and the population grew to over 100 at one point and I didn’t keep track of which fish were spawning . I would pull a mop every so often and put it in a 2 1/2 to hatch out and keep putting them into my two twenty highs when they were big enough . I suppose they were all cousins and Uncles and that may have been the reason for my large number of deformed fry but I don’t know for sure .

 

[Uberhoust]

The non-albino runts seemed totally normal other than the size, every albino was deformed in some way, and only about 1/4 of the albinos survived the fry stage whereas about 4/5 the non-albinos survived the fry stage. I tried to look at my past posts but did not find the post I was looking for but I think my fish are now about 2 years old.

The non-albino runts are 2" long and only about 3" tall. Whereas the normal fish are now averaging about 4 or 5 inches long and about 6 to 7 inches tall. These are just approximate going by memory now, but the runts almost look like they are a different species, their proportions look good, they are just smaller.

 

[Magnum Man]

I thought this was gone, didn’t see it for a few days… snagged it in a net today… all the rest are 4 inch fish… it looks to be eating, weather it’s digesting is another question… I put it back in the tank for the time being ( I was working on something else, and was just passing by… it looks like a mini

 

[Magnum Man]

It had been a while, since I had seen the runt, with no special treatment, I assumed it was as gone… saw it yesterday, it’s gone from guppy size to platy size, in the meantime, it’s siblings are nearing edible size, I could “can” them, or pickle them, the size they are now, not quite fillet size, and still in the 65 gallon, not in the grow out tanks… these were from my breeding, of bought fish from last year

The ones outside, were bought this spring, and are supposed to be the best farm grade blue tilapia, yet probably 25 % are pink, so are obviously hybrids… several of the big fish, are better than 10 inches long right now, so I’m thinking about butchering maybe the 2nd week in October

Not sure if the runt will get full sized with a much bigger investment in food, and time??? Definitely don’t want it breeding… but, while I have no problem feeding a predatory fish, or eating them myself, I’m not very good at just killing them… still have a rainbow in the TB tank that looks and acts normal, that I’ll have to cull in a week o so, when I begin sanitation of that tank

 

[Colin_T]

Runts don't normally get much bigger over time. It is usually genetic and all the food in the world won't normally make them full size.

 

[GaryE]

I'm soft hearted, and have grown a few runts out. They tend to have a lot more problems than size, and are generally short lived. They often develop deformities as they grow.

In many cases, they seem to have digestive issues, because while they eat, they get the oversized eyes of starving fish. The eye is normal but it looks huge and nothing grows properly around it. Whether this is a problem with organs or the production of digestive enzymes, who knows?
With Aphyosemion killifish, it's often the result of raising the fish at the wrong temperature, which affects their production of digestive enzymes. But that affects an entire group, not scattered individuals.

 

[TwoTankAmin]

Not all runts are the result of genetics. When I was breeding BN plecos I would move the babies to a 10 gal. to start growing. Feeding the youngsters was usually a food riot. There was lots of competition and some fighting. And I noticed that there was always a fish or two that seemed not to want to be involved in the fighting. So they would not compete for the food.

Over time the other fish grew larger faster and the few fish that did not want to fight did not keep up. I always sell the largest fish first. This meant the ones which were the strongest competitors for food would be removed from the from tank first. As the population thinned and the biggest fish were gone the small ones began to eat more and to start growing faster. They were not so much runts as cowards, they just did not want to fight for their dinner.

Yes, I also got the occasional true runt, But most of the time it was just cowards who grew normally when they did not have to fight for food. Basically, I think they knew if they were smaller than the others and they did not compete, they would not get beaten up. It was almost as if they knew staying small and not being aggressive would keep them safe from getting picked on. It seemed to work as a strategy for staying safe and over time they grew to the expected size.

 

[GaryE]

In some species, there are males who develop slowly, as a second wave. The first wave of quick growers die young. The second wave are the species insurance policy. They live way longer, and father a lot of babies as the bigger, aggressive ones drop dead. They're behind a lot of stories of sex changes and such, but their growth is in their genes.

They aren't runty though. Just slower, but without the large eye to head ratio, or any bodily deformities.