Hi there!

Short version: would it be wise to add a third Oscar to a tank to spread out aggression

Long version:
My two Oscars use to swim around together and were pretty friendly, we got them at the same time and they were the same size (A red albino and a red tiger) but lately the red tiger has has a huge growth spurt and has been bullying the albino a little bit, who is much smaller. I went back 10 pages here but didn't really find anything.

I use to keep Pakistani loach and the largest of the bunch was really aggressive to the other two, so we bought another 3 and the aggression was spread out between the fish. . But I realise Oscars and YoYo's are two very different kind of fish but I am wondering if the same principle would apply?

So far to try and stop the aggression I have tried re-arranging the tank (it worked for a couple of days) and adding real plants. I am at the point where I am considering finding one of them a new home, which I really don't want to do.

So basically what I am asking is should I put a third oscar into the tank to spread out the aggression (or perhaps another species if it'll help)

Hi Flippy, I have'nt been on the site for a long time myself but With what I have read, Three seems to be a bad number for Oscars. This was posted a few times before. Why this is I am not very sure. They might be trying to pair of ans if they do the third fish will come accross as a threat. The guys or 'Big Guns' of the site will I am sure put you right on this subject.... Jamie

jamesmillar wrote:


Thank's a lot Jamie, I didn't realise this I was just going from my experience with other types of fish.

I wonder if two more would be a better number or if it would cause the same problem, as you said I'm sure the Big Guns can sort me out.

I'll also point out that there is a common plec and a bumblebee in the tank, in my introduction thread I think I said my tank was around 40 Gallons, but that doesn't seem quite right to me.

So I just measured my tank and this is how big it is

19 inches heigh, 36 inches across, sides of the tank is around 15 inches (19x36x15) - I'm not sure how to use this to find out how many gallons it would be (I'm not use to working with gallons)

We've had the plecostomus for well over a year and he is still much smaller then the tank (I realise both he and the oscars will grow) but 40 gallons doesn't seem right for these fish to all be in the tank with plenty of room to spare. (Picture coming when I can find the cord to connect the pictograph generator and the typing machine)

Edit: okay so I'v done my research and it is 40 gallons. . We've had the oscars for at least half a year and they're around 5 inches and the pleco is maybe about 12 inches, the bumblebee is probably around the same but he usually stays in his giant bell ornament thing.

hey flippy

more often than a third oscar will DEF increase aggresion in your tank.

for a short term measure you could try the 'bgh time out bag' ?? this is where u take the fish which is doing the bullying, and put it in a net type container inside the tank. at this point u can rearrange all of yr decor in the tank so the remianing fish find new territories... after about an hour release the fish back, it will be so preoccupied with finding a new territory it will not do much bullying (again this is only a short term measure, not somthing that will get rid of aggressition completely)

also mate u REALLY need to start thinking about a tank upgrade..the aggression could stem form the fact ur tank is way too small...for 2 oscars plus plecs u should be looking for a FAR larger tank, if ur not in the posistion to do this maybe think about rehoming soem fish...normally we advise about 75 gallon tanks for ONE oscar, with a real min of 55 gal for one..

hope iv helped, Matt

askhammatt wrote:


you don't need the "big guns" most knowledgeable members will put you right on tank size. 2oscars and a plec in your tank is like putting 2 large men in a very small toilet and asking them to be nice to each other putting 3 or 4 in that tank will will certainly sort your problem out cos most likely they will die and you will have lots of room. a larger tank is the answer to your problem not more fish.

Your Tank measurements of 36x15x19 comes to a total of... Almost 37 gallons imperial and 166.5 litres.
On the home page of OFL look down the left hand side and you will see 'Tank Calculator'
It is a valuable piece of kit for your calculations on tank size. It will give you it in Imperial, US gallons and Litres.
As you will read, the norm for an Oscar is about 55gls per fish...

Thank's a lot you two. Glad I checked in here before I acted. I genuinely thought my tank was larger, argh, anyway.

As I said in my introduction post we are planning on moving a larger tank into the study once we've got it cleared out (we had a failed internet cafe, it's filled with computers and junk right now) I think the tank is filtered alright for the moment, in the mean time if it gets too bad I could move the smaller oscar into another tank that currently is home to our Gourami. . I don't know if the Ph will be acceptable, but it would be a temporary fix. The plan is to have this bigger tank in two months time (We actually had a larger tank before, the Pleco lived there on his own but it got a crack and the crack seemed to be expanding so we emptied it and ended up getting rid of it)

I have actually tried time out, but I usually only do it for a few minuted because I don't want to leave him there for too long.

They've lived together for this long I'm sure they can handle a little bit longer, poor guys, didn't realise I was doing so wrong by them. Thank you again.

A follow up question, do you think it would be okay for one 12 inch Pleco for the time being (meaning until he grows larger) or should I move him with the oscars once the new tank is cycled good and ready?

jamesmillar wrote:


Thank's for pointing that out to me! I didn't even notice it. I'll have it for next time now at least

So how big is ur new tank going to be Flippy? You said that a crack is appearing on on ur tank and getting bigger, This is due to eneven stress on the tank somewhere. When I set my tanks before I used to place them on polystyrene tiles to spread any uneveness. Even when placing a tank on a metal frame that is made for a tank a slight imperfection at the weld can cause great stress on the glass. You dont have to use polystyrene just something that absorb any unevenness.

jamesmillar wrote:


We're thinking around 500 litres, I'm not entirely sure what it is in Gallons (130 maybe?) We got rid of the tank with a crack, a friend took it (it was the tank the Plec use to live in). I'm not sure what he's done with it, probably going to sit in a shed for a few years. I actually have polystyrene under two of our tanks, it was a recent addition though. Just wish he had of known to do it before the crack happened

The place we were thinking about buying from actually shut down but there is an aquarium place we found recently, forget it's name but it's next to a car store, they seem to have a pretty large range of tanks. Once this blasted flu passes we'll head over and I'll get some prices and what not and keep you guys updated.

Remember you will have to cycle the new tank as well.
That will take an additinal 5-6 weeks.

WOW!!! What are they dimensions of your new tank then bud?