I often used to wonder and have been asked over the years what F1, F2 and WC mean in fish keeping. Now I am sure of the meaning of this its only fair to share it!
This all boils down to the genes land origin of the tropical fish. Generally a WC fish would refer to a Wild Caught fish. This is one which has been imported directly from where it was caught in its natural habitat and ended up in your tank. An F1 fish would be one which has been bred from 2 Wild Caught (WC) parents. Moving down the stack, an F2 fish is one which has been bred from both F1 parents and so on although you don’t often see fish advertised as F3 and onwards, rarely advertised as F2 to be fair.
You may be wondering why this is so important and why people state it. Keeping wild caught fish is quite tricky due to them being more susceptible to disease from the stress of being pulled from their natural environment however they may act slightly differently. It is also an important consideration when buying fish for breeding purposes. If you wish to breed healthy and strong fish, it is always best to have mixed blood lines. There’s an extremely high probability of wild fish having different blood lines however I’d you’re buying F1 fish to breed its advisable to get them from various sources or from batches from different mothers at different times so the mixture of blood lines is a higher probability.
Having non-mixed blood lines could be fine but could leave the fry they produce to become less colourful, more prone to disease or generally unhealthy. No animal should breed with its siblings!
Always be mindful that people have different perceptions of what is valuable and its often advisable to find out where and when a person got their fish from if they are claiming they are wild caught or even F1. Personally I prefer to buy F1 fish for breeding from different sources however some will prefer wild caught and often label them as such to give an excuse to increase the price.
Another type of fish which you may come across is pond raised. Around the African Rift Valley lakes there are various large ponds which once contained wild caught fish however are left to breed so you may end up with a wild caught when buying pond raised but could be various generations down the line so F3 for example. As they are raised next to the lake, personally I view these in the same light as a wild caught fish and should be treated as such when importing them and introducing to a tank.