Can Oscars max out at 9"-10"?

Jonnyakawombell

Piranha
MFK Member
Sep 10, 2010
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Hi I rescued 2 tiger Oscars about 6 months ago living in a 55g in not so great condition's, anyway they now live in my 420g and are kept in good conditions and fed well, I really like them as they both have fantastic personally, the only thing is they haven't grown at all since I've got them there still around 9" -10" but very chunky to be fair, so as the title says can Oscars just max out at that size? The other Oscars I've kept in the past would normally get to around 12" maybe even slightly bigger, many thanks.
 
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Sinister-Kisses

Aimara
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Jan 19, 2022
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NATURALLY - not very likely, no. They naturally get significantly larger than that. However, being crammed into a much, MUCH too small tank as they were will cause stunting, and if they were there for very long they might just be permanently "disfigured" and stay small. Poor fish, I can't stand people who do cram fish into way too small tanks. Good on you for rescuing them.
 

SilverArowanaBoi

Redtail Catfish
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Sep 21, 2023
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Hi I rescued 2 tiger Oscars about 6 months ago living in a 55g in not so great condition's, anyway they now live in my 420g and are kept in good conditions and fed well, I really like them as they both have fantastic personally, the only thing is they haven't grown at all since I've got them there still around 9" -10" but very chunky to be fair, so as the title says can Oscars just max out at that size? The other Oscars I've kept in the past would normally get to around 12" maybe even slightly bigger, many thanks.
Oscars, when properly taken care of, can max closer to 14-15 in. 9-10 is small.
 

Jonnyakawombell

Piranha
MFK Member
Sep 10, 2010
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With out knowing age and previous care, they may be full grown. I'm sure they are much happier in there new tank.
Yeah that's the problem I have absolutely no idea how long they were in that 55g, I mean it's obviously highly doubtful, but they could be 10 years old for all I know, and yeah they seem super happy and stick together at all times, there very personable and very very greedy lol, there like little dogs lol.
 

AR1

Redtail Catfish
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Jan 27, 2023
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Personality I've never had them to that sort of size but 12" -13" definitely.
That’s because Oscars are large fish with a big bioload, meaning they produce a lot of nitrates. Many fishkeepers struggle to manage this, which can limit the fish’s full potential.

In the wild, there’s essentially a 100% water change happening every second, keeping nitrate levels at zero. Achieving this in small tanks is nearly impossible compared to the natural environment.
 
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Jonnyakawombell

Piranha
MFK Member
Sep 10, 2010
345
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durham
That’s because Oscars are large fish with a big bioload, meaning they produce a lot of nitrates. Many fishkeepers struggle to manage this, which can limit the fish’s full potential.

In the wild, there’s essentially a 100% water change happening every second, keeping nitrate levels at zero. Achieving this in small tanks is nearly impossible compared to the natural environment.
Yeah totally understand, I was more talking about captive size, rather than wild sizes.
 

LBDave

Peacock Bass
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Nov 27, 2018
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You sure they are that length? Fish look smaller in the tank. When you take them out and actually see them it can be surprising. They may be an inch or so longer than you think.
I thought my oscars were 10". They were actually 12 and 13"
I have a jurupari that looks about 7-8". He's actually about 9"
 
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LBDave

Peacock Bass
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Nov 27, 2018
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NATURALLY - not very likely, no. They naturally get significantly larger than that. However, being crammed into a much, MUCH too small tank as they were will cause stunting, and if they were there for very long they might just be permanently "disfigured" and stay small. Poor fish, I can't stand people who do cram fish into way too small tanks. Good on you for rescuing them.
I don't agree. At least in my experience. I have seen oscars reach 13" in small tanks. I believe the small tank-stunted growth belief to be a bit myth.
 
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