If your strapped for cash ona tank look on Ebay or the classified section of this site. People are always selling big tanks cheap. You can probably get a whoel setup with everything you need less that half of what you d pay at a store. Good luck

How are you cleaning your filter off? And you really dont need to replace the cartridges until they fall apart. Changing them every week is not letting the tank cycle. Just rinse them in tank water (not tap water) and then put them back in the filter. The undergravel filter is useless, that is probably why the water is cloudy because Oscars are very messy fish and all the gunk gets stuck under the filter and it is not being sucked out by the other filter. Yeah, I thought that a 55 gallon would be good enough for my two oscars, I was wrong, by the time they hit 6" they were fighting really bad, so I bought another 55 gallon and they each have their own home and they are doing great. In order to house 3 Oscars properly you will need at least a 150 gallon tank, or 3 55 gallons. I would go with the 150 and be done with it. Best of luck with your little o's.I definitely appreciate all the feedback; I will try the pellets instead of the live food. I hope that may cut back on waste material. I have removed the cucumbers; but I am curious what the negative effects could be from them. At the moment I am using an under gravel filter in addition to a Marineland Penguin 100 bio-wheel power filter. It filters 100 gallons per hour and is adequate for up to a 20 gallon tank (according to the box).
I clean the filter off every 2-3 days and replace every week. I was advised in a reply to my original post to add another filter, but I may do an upgrade and replace the penguin. I hope that will help with the water quality. Unfortunately, I may have to wait a little while longer to upgrade to a larger tank form my current 10 gallon.
This brings me to my next question; how difficult would it be to make my own tank? I would love a 75 gallon tank, at least until they get larger. The largest my local fish store has is a 55 gallon model, which will only suffice for a short while. I don't wan't to get caught buying a half dozen tanks over time and wasting money; I would rather go for broke an get a tank that will last for a year or so. So anyone with some knowledge in tank construction please let me know what the best way to go would be; I know it will be some work but cheaper that buying. Thanks for any advice. Tom
I wouldnt call an oscar agressive, I would call them territorial. If you give them space, they can live with anything that wont fit in their mouth (assuming the "anything" isnt super agressive) There is always an exceptoin to the rule, I know there has to be a psycho oscar out there somewhere! lolYou should be careful though, oscars CAN get aggresive, just keep your eye on them as they grow bigger to be able to seperate as needed.
Good luck!
I'm glad you mention that. I was thinking the same thing, but forgot to postAre you using used filter media? If not, do you have any fishkeeping friends that could give you some used media? Also, used gravel would be a good start to get you through the next week or two. If someone has already suggested this I apologize for the repetition, I'm reading through the posts at work and may not have caught it.