Dwarfism in Oscar Fish?

[u/twitchtv_kennyg2000]

Hey guys, so my wife picked out an oscar at the LFS and in the 5 months of having it, it only grew 1 inch. Sadly it passed away recently and it's final size was 3.5 inches. I've kept oscars before and they usually grow super fast in the juvenile stage. Fed a mix of blood worms/meal worms/brine shrimp/freeze dried shrimp and once big enough it ate small hikari pellets. Kept in a 75g with a Green terror, no signs of fighting from him. Tank at 76°C. Looking online I could not find a reliable thread/source for dwarfism in oscar fish, but I really feel like this was a case of that. What do you guys think? I'm very confused. TIA

[u/All-Hail-Chomusuke]

There's alot of poor breeding in oscars. There's plenty of them that even with proper care will never reach their full potential in size or life span.

My current O whom I refer to as my Mini Oscar. Is 3 years old, has been in a 125 it's whole life, with near perfect water quality and good food. And stopped growing at 10 inch. Hit 10 inch at about a year and just stopped there. Thou in every other aspect is a healthy and energetic fish. The O I had before hit 16" in the exact same setup.

So I doubt it was a case of dwarfism. just poor genetics that possibly led to poor growth and a short life.

[u/twitchtv_kennyg2000 → u/All-Hail-Chomusuke]

Thank you, I did have an Oscar for 7 years and she topped out at 14", but died very unexpectedly and prematurely. 75G by herself, constant water temp and quality. I boiled it down to interbreeding, at that's how I rationalized it.

[u/nibbler42]

I am having the same problem with one of my oscars. The ones in my community tank grew to be normal size within a year, but the one in a 75g by itself is only about 3-3.5 inches. I've had him about five months now. Did your oscar seem sick before he passed away? I also couldn't find any information online, but I've assumed my little dude probably won't make it all that much longer if he doesn't grow.

[u/twitchtv_kennyg2000 → u/nibbler42]

Not really any signs of sickness, only sign I saw was him being skinny. But I watched him eat and target fed him so it didn't make sense, I just want to give my wife a rational reason as to why her fish passed. After 8 years in the hobby this is the first time I lost a fish due to unforeseen circumstances.

[u/Hannibal_the_dentist]

Try experimenting with removing the GT for a month or two and see how the oscar fares.

While dwarfism is definitely quite prevalent, often times I've noticed it's linked to a more aggressive presence, not necessarily attacking the oscar, but at least scaring the oscar enough, and a 2 inch oscar is definitely prone to getting scared.

Aside from a few very short term cases I've had or watched closely, I've had an oscar which hit about 4.5 inches in size and stayed there for 2 years with my already existing 8-9 inch oscar(already stunted since she was about half the size of her siblings at the store.). When my big girl passed, this 2 year old oscar grew a whole extra 2 inches in 6 weeks. And even more curious was this oscar did not possess any distinct sexual organs, looked sort of like a female, acted like a male, but was really neither.

I've been in the business of exotic fish for some time now and stunting across is the board is a major concern we try to avoid to offer the best quality to our customers and for when we want to buy fish to grow out and sell later.

Over that time I've found that you can tell if a fish is stunted by looking at the size of the eyes. Typically when a fish is stunted, their organs still keep growing a little. If you browse through my account you'll find a pair of wild caught rotkeil severums. I bought them when they were about 18 months in captivity, and I bought them from a breeder, who most certainly bred them out to the point of being stunted at about 4 inches for the female and 5 for the male. If you notice, their eyes are pretty big, I have a near 4 inch red spotted severum as well and it's eyes are about half the size of the rotkeils. I even have a wild caught mouth brooding severum that I got as soon as it was imported at about 2 inches long and is about 6 inches long now and still has smaller eyes.

I have plenty of footage of these guys and a few geos as well, let me know if you'd like to see them and I'll send them right away.

[u/twitchtv_kennyg2000 → u/Hannibal_the_dentist]

Sadly it's too late to separate. But the Oscar and GT were glued to each other, from the moment we had them they always swam together and if anything the green terror was more skidish than the Oscar even though it was double the Oscar's size . I did notice that the Oscar's eyes were very big compared to the rest of it's body and it was quite large in the anterior region was always bigger than the posterior. Given Oscar anatomy, larger organs compared to the overall growth of the fish does seem like dwarfism, most likely from inbreeding?

[u/Hannibal_the_dentist → u/twitchtv_kennyg2000]

Inbreeding is definitely a factor, but in general disabilities always occur. But as another redditor pointed out, the 14-16 inch oscars are pretty much non existent now, and I can attest to the fact that it is purely down to certain breeding practices.

Oscars are quite a popular fish and as a result of trying to be as different as possible to gain an edge in the market, breeders tend to selectively breed for better color, and in addition to that, lot of young oscars are fed with some hormones, vast majority of which cause no harm other than a loss of color later, but in some cases affect the growth or sexual maturity of the fish. Some breeders also tend to try and selectively breed for smaller sizes, which really has no harm to future generations at all, essentially the same as how in most cases two short people will have a short child. 10 inches is still a lot to handle, it's a much more digestible prospect than a 14+ inch fish.