My new oscars

Question
I would like to know what is the best thing to feed them and how often I should feed them. My aquarium is new and I have it in my bedroom. When I told the sales and where I was putting the yank, he suggested that I get the pump that goes on the inside of the tank, so it's quiet. I am wondering should I get a different pump? Also what temp should the water be? This morning my water was extremely warm. I had some tiny goldfish in the tank and they were half eaten this morning and now that water is cloudy. I know this sounds like a lot, but what do I do. Really want things to go well and be able to have strong healthy Oscars.  

Answer
Hi,
Oscars are very ambitious for a new fishkeeper, so you may encounter some problems. It is not easy keeping fish, especially large fish such as Oscars. Firstly, the tank needs to be over 300 litres. You must be aware they will grow to 12 to 13 inches at their adult size. If you already have the Oscars, take them back to the shop for a month or so while you get the tank sorted, otherwise they will most likely die. If it is under 300 litres, buy a bigger tank, or go with different fish for now. Any tank bigger than 150 litres is best with an external filter, which goes on the outside of the tank, as opposed to an internal filter, which is what you have now. The water should be between 24 and 27 degrees Celsius. You need a thermometer to go on the outside of the tank so you know when the water is too hot/cold. A decent heater, which is vital, will keep the temperature consistent.
The filter needs to be strong enough for the size of tank you have, remember.
The tank also needs to go through what is called the Ammonia Cycle. Cycling the tank takes 3 or 4 weeks and you cannot buy fish until after you have completed the cycle. Some people use fish to cycle, but a fishless cycle, using pure bottled ammonia, is better for beginners.
Find out as much information about cycling the tanks, and Oscars, as you can, before putting the fish in.
You also need to buy test kits for ammonia, nitrite and nitrate. During the cycle, monitor these every day. The ammonia should rocket, then the nitrite, then the nitrate. When the ammonia and nitrite are at 0.0, nothing over that, and the nitrate is under 20ppm, you can think about adding fish. You can buy bottled ammonia at bigger fish shops. Just follow the instructions on the bottle; it varies depending on what brand you use. If you know anyone with disease-free tanks, ask if you can use some squeezings from their filter, or just some gravel/ornaments. That will help speed up the cycle.
I recommend you join http://www.tropicalfish.site5.com/tfc/
as there are many friendly people willing to help you all the time.
Lastly, feeding live goldfish, or any other fish, to bigger fish is illegal. a lot of people do it unknowingly, so don't feel bad, but it is illegal, and also, not actually very good for the fish.
Good luck,
Kathryn

P.S. Please feel free to ask any more questions you need to.