So as a general rule of thumb you need 55gallons for a oscar and 25gallons for every other oscar that you add.

If you had to have 4 O's in a tank ten you would need a 130gallon tank right?

Now anyone that has kept fully grown oscars know that if you had to put 4 oscars in a 130g tank that the tank looks to small for them,so what is your thoughts on tank size and what would the bear min tank size be for 4 O's.

Just interessted as everyone has diffrent thoughts on tank size,i noticed yesterday at the LFS that the tag on the oscar tank says "min tank size 120 liters(27g) and i know for a fact that thats not big enough for one O.

I ignore what a lot of fish stores say. Anyone can open up a fish shop and start selling Oscars, you don't necessarily have to knows anything about them, they are just in it to make money, not all of them, but a lot of them.

A lot of people seem to agree that 55 gallons is big enough for one single Oscar. In my opinion, 75 gallons isn't big enough for two, I can say that confidently because I've kept two Oscars and 75 gallons and it wasn't big enough for them. I don't know who came up with adding an extra 25 gallons every time you add another Oscar. For Oscars are now 130 and tank, I wouldn't do it long term. I've got for Oscars in a 125 gallon tank at the moment, they are around 7 inches. These fish could nearly double in size, dread to think what it would be like in their them. If I was going to keep four Oscars, I would be looking for around 250 UK gallons. I'm not even prepared to put another two Oscars in my 300 gallon tank.

I cant really say as i havent got a full grown oscar yet. But i have seen them and they are massive. In my 100g (4ftx2x2) i plan on keeping 2 full grown oscars, 1 jaguar and 1 jack dempsey . My JD and jaguar are full grown (i think) and sometimes i look at the tank and think no way are 2 full grown oscar gonna fit. Its all down to space and how many water changes you are prepared to do. I suspect i am gonna end up with 1 oscar and the jag and JD. The rule i have is large weekly water changes and regular tests. When the water changes required to keep nitrates good becomes too much bother for me then its time for a fish to go

From a bio-load point of view I think that 4 Oscars in a 135USG is pretty easy to do. I currently have 4 in a 180USG and it's simplicity in itself. It's all down to filtration and PWCs IMO and every week my nitrates start from zero again. What I do is, gravel vac until I've covered the entire floor of the tank, which will take out approx. 50% of the water, then leave the syphon to carry on draining while I begin to re-fill. I set the re-fill hose to a speed that is fractionally faster than the syphon which means that it will re-fill, but it takes a while. This probably works out at about a 250% PWC when it's finished and I'm lucky enought that my house is configured so that the syphoned water can go straight out into the garden so no water is wasted. Since the syphon, and re-fill are at similar speeds this takes next to no effort at all and while waiting for the tank to re-fill i just watch TV. I water condition for 3 times what the tank needs to be safe and have managed to get it so that none of the filters (2 canisters and an internal) or heater need to be switched off. The only down side of this is that this can often instigate spawning, which you may or may not want, but it proves to me that the fish like it, they are certainly more active after I do one of these changes. As I said before, this always leaves my with a zero reading for nitrate too.

From a territory/swimming space point of view however, I can accept no responsibility

ive got a 200 uk gallon tank on the way and ive got so much i wanna out in there so thats why i raised the tank size question again.

oscars
silver dollars
tinfoils
gold severums.
Golden bristlenose.