Inbreeding: This is basically keeping a strain pure. The fish are kept closely related and brother and sister, father and daughter are routinely bred. A breeder will do this sometimes to fix a trait, such as a particular colour or shape. Mostly, you take the best male and female from the drop and breed them. Doing this can provide beautiful fish for years, provided the fish that you start out with are quality and you are lucky enough to choose not only the most attractive fish, but to pick fish as breeders that do not have an invisible weakness-for these will show up in the form of genetic defects, often looked upon as simply the result of "too much inbreeding". Take great care in choosing breeders; many times a strong body is the most desirable trait to keep an inbred line strong.
Line Breeding/Line Crossing: This method is also a form of inbreeding, however here you start by keeping the fry from two females (either from your new trio or chosen fry from a drop) separate, so that they form two distinct lines. Since you cannot mix batches, this takes more tanks. It is best to choose breeders differently for each line; for instance, in one line, you may pursue a large body mass, and with the other, you may concentrate on finnage. The purpose is to help maintain your established strain, since each line becomes distinct and more distantly related; also, you can have your own two lines to cross occasionally. When you want to increase the size in your fish, for instance, or make an outcross to avoid too much inbreeding, taking someone else's line to do this with is risky and you may loose the traits in your line that you have worked hard to achieve, as well as loosing the homozygous quality of your guppies.
Out Crossing: This is the opposite of inbreeding - the mating of fish that are unrelated to other. This creates what is called a "hybrid" guppy. "Hybrid" vigor may be seen in such fish-outstanding size, colour, and health. The genetic patterns