santoury;774289; said:Where did the Koi come up? I missed that.
Your tank is way too small for even JUST one oscar. I hope you do realize they get to approx a foot in length, each. And yes, they do eat fish, which is why they ate your red tail sharks.
The fact they did this suggests they are not even baby oscars, but youngsters, which means the tank must be pretty crowded already. This will result in very poor water quality, as well as probable stunting and ill health with your fish. I understand they might not be easy to get where you are, but what is more important, their health, or your obtaining them?
If the best you can do is a 18 gallon tank, don't keep Oscars.
ONE oscar is slightly cramped in a 55 gallon tank, for perspective.
.. so i never came to know abt this ... the oscars are of 1 inch each ! and everything seems to be pretty comfortable! lets see wat happens . its because of this reason alone that i have started feeding them very i mean very sparingly ! 

TicaL;774344; said:His sig said, 18.7 Gallon US - Just a beginner!
1 Tiger oscar 1 Copper Plate oscar 1 Albino oscar 1 Veil Tail albino oscar 2 Kois 2 Silver Dollars
Please tell me they're not all in there...
Bud8Fan;774385; said:Holy Crap !!
I have a 300 gallon tank and am only thinking of putting 2 Oscars in it !
Darudist;774440; said:Whoa dude, listen, the minimum tank for a single O is a 75 IMO. Some will say a 55 but when an O is a foot long and the tank is only 12" deep, need I say more. Before you think about getting anymore fish you need to get a least a 6 ft tank that is at least 18" deep. Post Pics of your setup!!!!