Oscar clarification questions

So...I will say this first....I need to quit planning tanks before starting work on getting my two 55 gallons up and going.....lol.

Anyway...I've always been interested in oscars. They seem like awesome fish to have. So I've been doing some research and just sort of want some clarification on some things I've read and questions I couldn't find the answer to.

(Little note-I'm looking for a minimum 75 but I've glanced at the facebook marketplace and man, I wish I had money now. Bigger setups on there for great prices. So, when I'm ready to buy, I will go bigger IF possible.)

75 gallon is ok for ONE oscar period? I know some people have said they can have tankmates...but from researching they say 3 silver dollars for this size tank and being as how they school....I would say probably not a good idea, right? Just the oscar? Almost everyone is saying this (well, some say 55...12 inch or bigger fish? No way will I do that). But I did read on seriously fish that they say minimum of 5ftx2ft base(not a clue on the gallon size of that).

So, first conclusion...minimum tank size 75 gallons (maybe??) For one single oscar and no tank mates.

I know they don't need tankmates. But if the tank is bigger, suggestions(including size tank) are welcome for more research for me. Lol. One fish I am interested in is the electric blue jack dempsey. Is that really a natural color? Not sure it would work with an oscar. I also like giant danios more than silver dollars (reg or spotted). I understand they may get eaten occasionally if not fast enough...but unsure if they would truly work too. Stress for then being a factor? Or, if big enough tank, 2 oscars?

More questions now...
Is sand substrate ok? I know they can dig. I'm ok with that. Mopani wood? Bigger size clay pot? I'm not sure if they would make a nice sized hide if it wanted to hide ever...if needed. Real floating plants? Plastic weighted plants for toys? I wouldn't mind if they got moved if it keeps it occupied. I've read they can be mean even to anubias.

Diet clarification.
Good quality staple floating pellet. Omega one brand maybe? Haven't looked into brands yet. Lol.
Occasional shrimp/krill from grocery store?
Earthworms, mealworms, crickets? -Walmart has earthworms and sometimes crickets in bait section. Could these be used? I'm thinking maybe not?
Mostly this....fruits and vegetables? I've only read/watched a couple of things that said to feed this.

Feedings itself...regular daily schedule? Once only? Or smaller amounts 2-3 times a day? Any days off? Some have said to mix it up. Feed multiple times, skip some feedings, skip days. Also amount to feed is when the agressiveness towards the food is declining because they are pigs. But if there are tankmates, not sure if that's a good idea?

Cycling!!
If no plants for oscars...and it's minimum 75 gallon....everything set up right, do I have to "cycle" with ammonia first if I'm only putting one small oscar in it?

If it's bigger and can have tankmates...add them first?

Can you quarantine a small oscar in a ten gallon for 4-6 weeks? I know it depends on size and I know they can grow very very fast. An inch a month I think?

Ok...I think that's everything I can think of now. I know it's a messy fish and needs good water changes, great filtration, great water quality. Heat around 78-82, so 80 probably.

I know nothing about oscars I'm afraid, but playing with the calculator on here and using that tank footprint from Seriously Fish -

A tank with a footprint of 5 ft x 2 ft with the following heights gives these volumes:

12 inches high - 75 gallons
15 inches high - 94 gal
18 inches - 112 gal
21 inches - 131 gal
24 inches - 150 gal.


Google suggests that the most common size for 75 gallons is a 4 ft x 18 inch footprint.

essjay said:

I know nothing about oscars I'm afraid, but playing with the calculator on here and using that tank footprint from Seriously Fish -

A tank with a footprint of 5 ft x 2 ft with the following heights gives these volumes:

12 inches high - 75 gallons
15 inches high - 94 gal
18 inches - 112 gal
21 inches - 131 gal
24 inches - 150 gal.


Google suggests that the most common size for 75 gallons is a 4 ft x 18 inch footprint.

Click to expand...

So...is this why everyone says a 75 is ok for one oscar then? Even though it's a different base dimension? I know an oscar wouldn't want to live in 12 inches of water I'm sure. I'm hoping where I could come up with the money that there will be great deals then and I could get something bigger than 75. But except for seriously fish, almost all fish keepers say one is ok in a 75. I've watched and read a lot of things and Rachel o'learys video on her species spotlight where she showed her own oscar, I believe it is a wild caught or at least wild type. She used to keep it in a bigger tank and tried tank mates but he killed them all. Now he lives happily in a 75 and actually hasn't killed his catfish tank mate. He's at least 10 and going strong still.

I'm no expert on Oscars so I won't pretend to be. However, I have seen Oscars in 55-75~g tanks in fish stores but like Beta's in little cups, it seemed cruel - they were such a big fish they could seemingly barely turn around let alone have enough room to swim around much. Personally I think for such large fish you'd need a 125g or even larger (just my $.02).
(Maybe sit on this one until the other tank projects get real).

I've got my oscar in what I call a 65 short [40b).

He was starting to touch both sides in his 55, he actually looks smaller in his 40, it is mostly about the footprint.


I know what they say now, but thirty years ago I had a oscar, pacu, Jack Dempsey's, convicts, firemouth, Jews and tiger barbs in one 55g and they all did just fine

He gets water changes about every 5 days

He's 13"

AbbeysDad said:

I'm no expert on Oscars so I won't pretend to be. However, I have seen Oscars in 55-75~g tanks in fish stores but like Beta's in little cups, it seemed cruel - they were such a big fish they could seemingly barely turn around let alone have enough room to swim around much. Personally I think for such large fish you'd need a 125g or even larger (just my $.02).
(Maybe sit on this one until the other tank projects get real).

Click to expand...

Yeah, that's what I plan to do. I just wanted to do research before hand so I can think about it more and of course....I don't have money for it. Lol. I joined an oscar group on Facebook and they all said 75. And I would need to be fish less cycled first and have a couple of aquaclear 110s on it for the bioload. But...if/when I have the money and Facebook marketplace has deals like they have now...it will be bigger. Maybe a 125. Then I could have 2 maybe!

Another thought though....where would I put it....*looks around to see what furniture might need to be moved out....* lol. I'm well under way to multiple tank syndrome!

Toney said:

I've got my oscar in what I call a 65 short [40b).

He was starting to touch both sides in his 55, he actually looks smaller in his 40, it is mostly about the footprint.


I know what they say now, but thirty years ago I had a oscar, pacu, Jack Dempsey's, convicts, firemouth, Jews and tiger barbs in one 55g and they all did just fine

Click to expand...

You may say they did well but....we don't really know for sure. I wouldn't put a fish that has a potential to grow over 12" in a 12 inch wide tank. I can kind of see a 40 breeder but that just seems too small to me too. It can turn around, but wouldn't be able to swim much. And I'm imagining more water changes are in order being a smaller tank? Great looking oscar though!

Heck oscars don't swim all that much, he mostly watches tv or is trying to get my attention so I will feed him some more

Toney said:

Heck oscars don't swim all that much, he mostly watches tv or is trying to get my attention so I will feed him some more

Click to expand...

I dunno, some in videos of bigger tanks swim around. But they have individual personalities. You must have a uh...tank potatoe...lol. question...some people at the oscar group are telling people to "play" with their oscars. How exactly do they do that?

Water changes, yeah.... I'm pretty sure he poops twice as much as he eats... and all of it is to big to fit through the strainer.... I've removed mine so the poop doesn't get to deep.

Do you "play" with your oscar? People on the facebook group were mentioning it but didn't give any details. One thing I read said they gave them ping pong balls to chase around. But other than that? I'm not sure. Lol

It's fun watching my two youngest grandkids putting their faces against Oscar's tank and getting him all excited.

Oscar does like to move stuff around in his tank and will bite the crap out of you for trying to put it back right...

I don't want to spoil it for you, but cichlids are pretty intelligent. And you want to confine one of those to living solo in a small tank for it's whole life?

They don't swim around much, because they are bored to death, overfed and their is no space to swim anyway.

Toney said:

I know what they say now, but thirty years ago I had a oscar, pacu, Jack Dempsey's, convicts, firemouth, Jews and tiger barbs in one 55g and they all did just fine

Click to expand...

Are you serious? Maybe as long as they were juvenile and only a few cm longs or you have seen a fish who did fine for real.

Just yesterday, I saw a pond 4x2 m. And the dominant cichlid (some african, smaller than an oscar) was using the whole footprint of the pond! If the pond was larger it would have used even more space. And that is what I have seen with all large tanks, I have been able to observe. If you give the fish space they will use it.

Just my 2cents

The Jack Dempsey's regularly spawned the Oscar was fully grown I did swap off the pacu after a couple months.


You know back then a 55 was a really big tank.

Post #13 has hit everything bang on.

AS 75 gallon tank, which assumes length 4 feet and width 18 inches, is absolute minimum for one Oscar. This fish has a maximum length of 45cm/18 inches, usually around 30cm/12 inches in aquaria. A healthy Oscar will grow at a rate of approximately one inch per month with proper care.

Fish are living creatures that deserve adequate space. A fish forced to exist in a bare tank that is small for the species is not humane. I'm sorry, but there are inexperienced members here who could easily come away from this thread with the absolutely wrong idea if it is not made clear.