Oscar fish bare minimums.

I would like to start a thread on the bare minimum size tanks for an oscar. I see that on threads from other sites and even this one over the years have gotten the question of tank sizes for oscars. Often I disagree with the recommendations. I am aware that I am new to fish keeping, so let me know why my reasoning is wrong, if it is.

I have found that you can look up tank size requirements for oscar fish all day. You will hear various answers. You can find 55 gallons as a bare minimum for one oscar, 75 gallons for one, or even 100 gallons for just one oscar. Now, you will more often than not hear the 55 or 75. Though I have read my fair share of posts saying a minimum of 100 gallons. I cannot for the life of me figure out why. I agree that a 55 gallon is minimum for an oscar. Though I would say that someone can comfortably house two in a 55 gallon. Here is why. A standard 55 gallon tank is 48" long, 12" front to back, and 21"-22" inches tall. The average oscar will max out in size at about 12", maybe even smaller. Though I personally see people throw around the 16". That is absurd. One would be hard pressed to find an oscar that is captive bred from Petsmart, Petco, or wherever that grows to be 16" long. Maybe a wild oscar. The most people will see from a captive bred oscar is 13"-13.5", and that is extreme. One would more likely see a 10" oscar than one bigger than 12".

So that brings me to my question. Where is the problem with two oscars in a 55 gallon? I know that if they get longer than 12", then you should move it. I see no reason to bank on your fish growing to an odd size like that though. Also, oscar fish are very relaxed and not too active. Or at least that is what I have seen from all of the ones I have ever met. It seems to me that if someone has proper filtering for the two oscars and they are peaceful, then they can coexist in a 55 gallon easily. Let me know what you think!

 

I don't know anything about Oscars, but would have thought them being territorial might be a factor?

 

Hi, I read all you said. I have an Oscar, one Tiger. I have large tanks, several. In order to buy and house reptiles, I made a decision to use my 125g tank for the lizards, Basilisks.
My Oscar is a year old. He is about 10 inches long. I put him in a 55 gallon tank and I hated it. He had little to no room to turn and basically, imo, appeared cramped for space.
There was also the filtration issue. I feed him frozen worms, Oscar pellets and sometimes shrimp or fry. It was a bloody mess before a week was up. He now resides in a 150 gallon with a JD and a few clowns and the group is doing awesome. There are also three canister filters for filtration on this tank and it is crystal clear.
So, could I have kept him in that 55g, possibly but I fear he would have had a much shorter life span due to water quality. Does the current tank appear empty? No, it looks like an appropriate size for a semI grown Oscar.
Finally, it is my opinion that in keeping fish, we should strive to give them optimum conditions if this is possible.

 

I don't know anything about Oscars, but would have thought them being territorial might be a factor?

Not to my knowledge. I have seen plenty of tanks with multitudes of oscars. My only guess is their bioload, but with proper filtration that should not be a problem.

 

I saw the Oscars and thought 'Gold fish'. Why? Because the bigger the fish, the more waste it produces. A smaller tank = a higher maintenance regime. Also, would you be happy kept 24/7 in a 10 by 10 room, which would include your washing facilities, lounge, kitchen and garden all in one? Yes, I know they aren't Goldfish, and i'm comparing them with a poop factory, but that's exactly what would happen to a 55 gallon tank and two Oscars, not to mention if they fell out with each other, no where to go to get any peace.


Read the part about companionship, that begs to differ.

 

I saw the Oscars and thought 'Gold fish'. Why? Because the bigger the fish, the more waste it produces. A smaller tank = a higher maintenance regime. Also, would you be happy kept 24/7 in a 10 by 10 room, which would include your washing facilities, lounge, kitchen and garden all in one? Yes, I know they aren't Goldfish, and i'm comparing them with a poop factory, but that's exactly what would happen to a 55 gallon tank and two Oscars, not to mention if they fell out with each other, no where to go to get any peace.

I really don't think that tank size is an issue. If you have ever seen a single 12" oscar in a 55 gallon, you would probably agree that there is enough room for more fish. You are right that they could fall out, but that is a risk you take no matter what size tank you have. Unless you have a 200+ gallon tank then there is really nowhere to hide from the other fish if it is hellbent. Like I said previously though, so long as you have proper filtration, then it should work.
Here are another two oscars in a 55:

 

I find both those videos very sad.

Can someone put 2 Arowanas in a 90g or 2 Oscars in a 55. Sure.
Should they, Imo, no,

Fish that large shouldn't have to swim around in itty bitty circles.

 

Your reasoning is flawed. The main reason Oscars don't grow more than 12" is because they're in 55 gallon tanks. I kept and bred Oscars for 20 years. In 180 gallon tanks (6x2x2) they max out at an average of about 15". In 240 gallon tanks (8x2x2) they will push 18".

Keep them in 55 gallons if you like. The 100-gallon-for-one rule just allows them to achieve more of their potential.

There is of course genetics involved - not everyone will grow to the same size - but most Oscars will exceed 15" given a big enough tank, IME.

My own recommendation for this 18" species is 120 gallons for one, or two, 150 gallons for 3, 180 gallons for 4.

 

I find both those videos very sad.

Can someone put 2 Arowanas in a 90g or 2 Oscars in a 55. Sure.
Should they, Imo, no,

Fish that large shouldn't have to swim around in itty bitty circles.

I guess I see what you mean, but the fish seemed happy to me.

Your reasoning is flawed. The main reason Oscars don't grow more than 12" is because they're in 55 gallon tanks. I kept and bred Oscars for 20 years. In 180 gallon tanks (6x2x2) they max out at an average of about 15". In 240 gallon tanks (8x2x2) they will push 18".

Keep them in 55 gallons if you like. The 100-gallon-for-one rule just allows them to achieve more of their potential.

There is of course genetics involved - not everyone will grow to the same size - but most Oscars will exceed 15" given a big enough tank, IME.

My own recommendation for this 18" species is 120 gallons for one, or two, 150 gallons for 3, 180 gallons for 4.

Interesting. My brother had one in a 75 gallon and he maxed at 12". I have never seen one in my LFS over 13". Though I would imagine that is true for any fish. Just like arowanas grow much bigger in ponds than in tanks.

 

Not a fish, but a comparison. My horse is on box rest for 4 weeks. Meaning he's stuck in a 12 by 12 box with nothing but a haynet for company and a water bucket. He can be walked, but not ridden or turned out. He has three walls and a window. Through the window he gets to see, hills and trees. But not other horses.
How can you keep a bored animal from getting depressed? Get two I hear you say? But then, when one is bored of the other, they have no where to go to get away.
My horse has no choice on the subject, vets orders. You can make a difference for your fish by giving them the space to behave as they should. A larger tank would allow that, and they will find a way to show it.

 

Interesting. My brother had one in a 75 gallon and he maxed at 12". I have never seen one in my LFS over 13". Though I would imagine that is true for any fish. Just like arowanas grow much bigger in ponds than in tanks.

You don't see many over a foot here either, because people generally keep large fish in tanks that don't allow them to grow any bigger. Most if not all Cichlids, and most fish, are restricted like this.

 

Not a fish, but a comparison. My horse is on box rest for 4 weeks. Meaning he's stuck in a 12 by 12 box with nothing but a haynet for company and a water bucket. He can be walked, but not ridden or turned out. He has three walls and a window. Through the window he gets to see, hills and trees. But not other horses.
How can you keep a bored animal from getting depressed? Get two I hear you say? But then, when one is bored of the other, they have no where to go to get away.
My horse has no choice on the subject, vets orders. You can make a difference for your fish by giving them the space to behave as they should. A larger tank would allow that, and they will find a way to show it.

I understand what you are saying. Thank you for explaining why the minimum tank requirements are as they are.

You don't see many over a foot here either, because people generally keep large fish in tanks that don't allow them to grow any bigger. Most if not all Cichlids, and most fish, are restricted like this.

Apparently, but even most fish sites you read say oscars are 12".

 

Apparently, but even most fish sites you read say oscars are 12".

My opinion on "minimum tank sizes" for large fish is that they are compromises. If you give a realistic minimum for most 12"+ fish, very few people would be able to keep them. But they would all know someone with one in a '55', so they would do it anyway, and not listen to any more advice from that source. Nobody seems willing to take that step.

Another compromise is the lack of weight behind the advice given for large shoaling fish. Pacu and Semaprochilodus are good examples... "they grow huge, a shoal is out of the question, so just keep one"... huh??

 

TyGuy320

This is a very interesting topic .
Thank you for sparking this conversation.

 

There's the scientific way and there is looking at the wider picture. Weighing everything out in your head, and putting the animals welfare first above all things.

 

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This is a very interesting topic .
Thank you for sparking this conversation.

That was the goal

 

There is an interesting, and I think informative divide here; those who have kept oscars favour a larger tank.
I can't recall keeping an oscar in less than a 72" tank, but this bit might be of interest: a friend of mine and her hubby kept two in a 55 gallon tank, and she had gone through 3 pleco's who were killed by her oscars prior to her being given a 150 gallon tank. She now has no difficulty maintaining her plec with her oscars.
Given their size, I find oscars to be rather large, very greedy/messy, and very lovable fish, far more gentle than a similarly sized Central American cichlid is likely to be. That is assuming a properly sized tank, of course.
Best to you, rick

 

imo opinion small tanks that oscars are being kept in (55g) is the reason they never exceed 12". I have two oscars in a 200 gallon tiger (oscar4") (lutino5") and they are the only fish in there.That's just my 2 cents

 

Water quality plays a huge role in fish size and health. Often when Oscars don't reach their full potential in size, water conditions are to blame. I don't know how it would be possible to keep nitrates down in a 55 gallon with two Oscars. Even with one Oscar in a 55, it's going to be very hard to keep nitrate at an acceptable level.

 

I'm not indicating that oscars should be kept in small tanks since swimming space, territory and comforts should be highly considered, though good genes, and diet are also important for maximum size growth. Even in a small tank, as long as good food, good genes, and water quality is maintained, the fish will grow to full size.

 

.....Even in a small tank, as long as good food, good genes, and water quality is maintained, the fish will grow to full size.

I disagree, and all of my experience tells me otherwise. Tank size always plays a part. An experienced aquarist can grow fish bigger in small tanks, but there are limits.

 

I disagree, and all of my experience tells me otherwise. Tank size always plays a part. An experienced aquarist can grow fish bigger in small tanks, but there are limits.

I know it may seem odd, though this has been proven in lab controlled tests.

 

I know it may seem odd, though this has been proven in lab controlled tests.

Do you have a link? Proven for which species? So what was the minimum tank size they found they could grow an Oscar to 18" in? 2'? 3'?