Often times, symbols will be mixed - for example, a Koi fish with a tiger's head will symbolize someone who is generally at peace but who knows his or her strengths and will fearlessly protect themselves and their families at any cost.
When the koi in the tattoo is shown swimming upstream, it can be used to mean that the tattooee is still struggling with his problem, whereas a koi swimming downstream implies that the tattooee has already overcome his difficulty.
As you can see, the beauty of koi fish makes them a natural choice for tattoo inspiration, but the fact that these designs hold symbolic meanings really dovetails with what tattoos are all about.
The two yin and yang koi complete each other and create a perfect balance of the negative and positive energies of chi energy, which is the life-force of all things on earth.
In fact, one of the oldest Chinese legends tells about a brave koi that fought its way upstream to reach the Longmen's Dragon Gate, a series of caves in the mountainside bordering the Yi River.