Oscars,will be the most important stage that your aquarium will go through. Get it right and it will set you on the road to a healthy tank for your Oscars to live in for a long time. Get it wrong and it could lead to you getting out of the hobby before you even got the chance to watch your Oscars grow. In my opinion there are three things you need to cycle your tank. Patience patience and what was the other one oh yes patience. I would hazard a guess that a high percentage of new people to the hobby fish keepers do not have the patience to wait until the tank is matured fully for the needs of the new fish. This has resulted in an explosion of products to cycle your fish tank as quickly as possible. In the 40 years that I have kept fish I have never felt the need to use chemicals or starter bacteria. Way back when i was a lad I simply listened to my uncles advice. This was have "patience with your tank and wait for it to mature before adding fish". I always listened to him and thanks to that I have never had any disasters when setting up tanks. Why then is cycling so important to your tank. first of all we need to know what we mean by cycling the tank. A cycled tank is one that has sufficient bacteria to cope with the waste products that your fish produce . For anyone who is not familiar with how waste is produced and dealt with by bacteria then type in "the nitrogen cycle for fish tanks" on any search engine for a comprehensive explanation. A cycled tank is even more important when keeping Oscars because of the amount of food that they eat and the amount of waste that they produce in comparison to other fish. So here is my advice to anyone who is about to set up a new tank.
Set up your tank with your filtration running and the substrate in the tank(leave the decor till later), use your patience, spend some time thinking about what decor you would like whilst you are watching the tank mature and then add the decor. Spend some more time thinking about what fish you are going to get and what stocking levels you would like and finally spend some time wondering around all those fantastic fish shops in your area looking for the best possible stock you can find. After two weeks check your ammonia level, if you have an ammonia reading then leave the tank alone, use that patience again at this stage.
After a third week check it again, if you have an ammonia reading its still not ready, although by now this should be pretty unlikely as your tank should have matured by now. What you should have is a fully cycled tank with crystal clear water. This is exactly what your new Oscars will need.When this is achieved and only then,purchase your fish.
Introduce them slowly with the lights off. If youve bought Oscars then don't feed them for the first two days. They are ready to feed when they rise to the top of the tank when they see you coming towards the tank. Feed them sparingly for the first week so that you don't overload the filters. If you add fish before a tank is fully cycled then the chances are youll have problems and in many cases this often leads to people giving up on keeping fish before they've had the chance to see what a wonderful hobby it is. Remember PATIENCE, PATIENCE AND PATIENCE.P-

excellent post

I was always under the impression that you needed some source of ammonia in a tank to cycle it (ie fish). With no fish where is the source of ammonia for the filters to cycle?

No you dont need to add anything i have never added anything to cycle a tank. Id rather spend my money on the fish than on additives.

So how does an empty tank cycle. You can only get the good bacteria in a filter when they have a food source. An empty tank surely has no food source so no bacteria which means it wont cycle?

The process is started by airborne particles. Its the reverse of what happens if you leave a bucket of water outside to go bad.I can definitely say that when i started keeping fish 40 years ago as a kid there were no bacteria treatments around to aid cycling. In fact there were no high powered filters like we have today, my set ups relied on box filters and under gravel filters.