How Soon Can I Add Fish?
It is best to leave a newly filled aquarium about a week before adding new fish, this will allow the temperature to stabilise and water chemistry to settle. Leaving the tank any longer than this will have no benefit unless you are carrying out a cycling process.
Cycling is the process of maturing a tank so that the filter is capable of processing the waste products created by your fish. There are several methods of cycling and the one you use will affect how many fish you can add and how often you can add them. For more information read our article on Cycling
Many different aquarium shops will give different advice on when you can add fish to your tank so it can be confusing who to trust when one source says you can add fish after 24hours whilst another says two weeks. In general, a week is fairly standard practice but if you have a trustworthy retailer, they may have methods which will allow you to add your first tropical aquarium fish more quickly.