Stunted Oscar

[duanes]

There's your reason.

I agree with this.
I normally do 30% to 40% water changes "every other day" on cichlid grow out tanks.
I know some breeders that do 80-90% per day to get good growth
All cichlids produce growth inhibiting hormones, that in small tanks ( I consider tanks of 50 gallons or under, small) build up to a stunting level, and are only removed with lots of frequent water changes.

 

[tlindsey]

It's many variables but what the important question is did you test your water parameters in the aquariums during the Oscar's growth. Some species fish will grow but others may not in let say for example high Nitrate or harder water. The Oscar is from SA but Vieja and JD CA species different water requirements.

 

[tlindsey]

Are Oscars more susceptible?

Yes

 

[duanes]

It's many variables but what the important question is did you test your water parameters in the aquariums during the Oscar's growth. Some species fish will grow but others may not in let say for example high Nitrate or harder water. The Oscar is from SA but Vieja and JD CA species different water requirements.

Agree
and because as simple aquarists, we don't have the ability/equipment/knowhow, to test for these hormone, ...
using nitrate is a good indicator of their buildup.
I find if your nitrate level is above 10ppm, that is a significant build up, if nitrate is 20 ppm or above more the chance of HLLE increases, or if 40 ppm, stunted growth and chronic HLLE infections are almost inevitable.
Beyond growth inhibition, for oscars (and some other South American soft water species), high nitrate in conjunction with a pH of 7.5 or above increases the chance of HLLE (hole in the head disease) as the oscars mature.
In their S American waters, the naturally low pH, and tannins inhibit the HLLE disease bacteria.
Central American cichlids like Vieja, that have evolved in high pH water have (over millennia) built up immunity to these naturally occurring bacteria.

 

[Gourami Swami]

I agree that it's important to check your water, and it's possible if there was higher nitrate that it stunted the fish. But I also think it's possible the fish is just a runt, or was stunted before you purchased it. Working at petco for years, I have seen oscars kept in abysmal conditions, too-small tanks with bi-monthly water change, that kind of thing, that still grew to be pretty large fish in those conditions.
I would check your nitrate thoguh, nitrate creep is a real thing and if the tank never got above a 25% water change it could have crept up quite high.

 

[Rocksor]

Yeah, Ive never heard a 25% weekly not being enough or excessive. He wasnt with any aggressive fish. He was with guppies and a Ram

Also, if water change routine is the reason, why is that the only fish stunted? I have a 9" vieja that grew fine, and an 8" JD. Are Oscars more susceptible?

25% weekly doesn't mean much if your nitrates are way above 20ppm. It's not about the percentage, it's about the nitrate levels and total dissolved solid levels. So in a 20 long for 6-7 months, it's only getting 5 gallons of water changed every week. Now if the oscar had been in a 40 or 60g, then I would think of it being a runt a possibility.

Oscars are a soft water fish, meaning that the total dissolved solid levels are way down compared to hard water fish like Vieja and JD. That 200-300ppm difference will cause the oscar's body to work harder at osmotic regulation. More work, means more food, and less energy for growth.

I've had an albino/lutino oscar a couple of times at the same size, the last one being a petsmart oscar, and in 8 months they were both 6-8" total length (including the fin). The larger the tank you start out with and more water changes, the faster the growth do to dilution of pollution

 

[RD.]

In agreement with the others. IMO nitrate toxicity is a misnomer. But in a glass box, when one sees higher nitrate levels, they typically also see higher levels of overall pollution, including dissolved organic compounds, along with elevated levels of bacteria. The latter is what weakens the fishes immune system, not the nitrates. In this case it may have also caused a reduction in growth, whether the fish started out as a runt, or not.

Also, what exactly are you feeding this juvenile fish, besides guppies?

He wasn't with the larger fish until last week. The oscar had access to all the guppies he wanted while being the larger fish. Is it food? is it tank size? or is it water change routine as you suggested? I hand feed him, he gets fed.

 

[jjohnwm]

I think that a lot of factors are probably at play here; insufficient water changes are undoubtedly an issue, along with possible problems regarding the quality of tap water you started with. Perhaps quality of food being used?

But I don't believe that those issues alone caused such severe stunting. Contributed to it, certainly, but I think that your fish was a runt, plain and simple. As pointed out by Gourami Swami above, plenty of fish (oscars and otherwise) in horrendously undermaintained tanks are seen to grow much faster and larger than yours did. They don't grow as fast as they would under ideal conditions, but they still grow much more than yours.

You can change and improve your maintenance regimen to improve things, but the genetic element is uncontrollable.

But, look at the bright side: nowadays, culls...fish that throughout most of aquarium-keeping history would never have been allowed to live due to deformities like bent spines, distorted bodies, etc...are actually in demand. A "Dwarf Oscar" would be a marketplace hit, guaranteed. Yours could be the original source, the Point Zero specimen that turns the aquariological game on its ear.

I wish that were entirely a joke, but...somebody's probably feverishly working on it right now.

 

[RD.]

The guppy feeder comment is what raised my eyebrow. No mention of what else if anything was being fed in that tank. Oscars, like most tropical fish require certain nutrients in their diet, and sans a proper balance of various nutrients can certainly result in stunting. Something as simple as a lack of Vitamin C can cause serious consequences in the growth & overall health of a juvenile oscar.

Oscars, Astronotus ocellatus, Have a Dietary Requirement for Vitamin C | The Journal of Nutrition | Oxford Academic (oup.com)

Abstract
We found that vitamin C is an essential nutrient for an Amazonian ornamental fish, the oscar (Astronotus ocellatus). This was demonstrated by the absence of L-gulonolactone oxidase activity, the enzyme responsible for the biosynthesis of vitamin C, in liver or kidney of oscars and by a feeding trial in which oscars without vitamin C dietary supplementation developed clinical deficiency signs. Fish weighing 29.2 ± 1.9 g were divided into four groups, and each group was fed a casein-based semipurified diet containing 0, 25, 75 or 200 mg ascorbic acid equivalent (AA)/kg diet for 26 wk. Vitamin C was supplemented in the diets as L-ascorbyl-2-polyphosphate, a mixture of phosphate esters of ascorbate, which is more stable to oxidation than AA. At the end of 26 wk, fish fed no AA had significantly lower weight gain than fish fed the AA-supplemented diets (P < 0.05). Oscars without dietary AA supplementation gained only 37% of their initial weight, compared with 112, 102 and 91% gained by fish fed 25, 75 and 200 mg AA/kg diet, respectively. After 25 wk without dietary supplementation of AA, fish began to develop clinical deficiency signs, including deformed opercula and jaws, hemorrhage in the eyes and fins, and lordosis. Histology indicated that fish without AA supplementation had deformed gill filament support cartilage and atrophied muscle fibers. Collagen content of the vertebral column was significantly lower in fish devoid of dietary AA (P < 0.05). Liver AA concentration varied in proportion to dietary concentration of AA. The minimum dietary AA concentration tested in this study, 25 mg AA/kg diet, was sufficient to prevent growth reduction and AA deficiency signs in oscars.

 

[RamMac]

I agree with this.
I normally do 30% to 40% water changes "every other day" on cichlid grow out tanks.
I know some breeders that do 80-90% per day to get good growth
All cichlids produce growth inhibiting hormones, that in small tanks ( I consider tanks of 50 gallons or under, small) build up to a stunting level, and are only removed with lots of frequent water changes.

Great theory, however the way here was never a question as he is clearly already stunted. I am curious as to how much growth is expected now that it's stunted.
Also, as I've said, this is the only fish that is stunted, so water changes or parameters only affect oscars?