SELECTING TOSAI

Tosai in the koi hobby is considered to be koi under the age of one year. In many cases, many Japanese breeders may also consider Tosai to be koi under eighteen-month. This is what they would consider as Jumbo Tosai. In Japan, many breeders take pride on the culling selection (senbetsu) of their Tosai. Their process is very tedious and koi that make it through these stages are often sold to dealers that carry import koi. 
So what should we look for when picking out Tosai? When we are looking at a Tosai, the basic anatomy of the koi should be the top priority. Is this Tosai something that you will like in the future? How will the koi develop in the future? These are all questions you as a pond owner should ask yourselves before purchasing your Tosai. In addition, you should talk to your koi dealer about the koi's bloodline and their opinion on the development of the koi you have selected. 
Basic Anatomy:
The basic anatomy of the koi should be the first thing that is examined before purchasing your Tosai. What do we mean by this? Check your koi to see if they have both of their pectoral fins, both of their anal fins, both of their gill plate, and both of their eyes are all intact. Any reputable dealer should already have their koi's checked prior though, so this shouldn't be too much of a concern.   
Body Conformation:
The next step we look for in a Tosai is the body conformation. We believe this is an important step because we are looking at the koi long-term. Keep in mind, when selecting a Tosai you are selecting it for its potential in the future. A Tosai has many features we need to look out for, the first part we should look at is the "shoulders" of the koi. Yes, koi don't have shoulders, but we are talking about the part of the koi from the head to the start of the torso. This midsection part of the Koi should be pronounced and have a broad "shoulder." When a Tosai begins to develop, we look at this part for its potential to grow. The bigger/ stronger the "shoulder" is, the more we can be confident in its potential growth. The next part of the body we must examine is the head. While looking at the head, we should notice how the proportion is compared to the rest of the body. If the head is smaller than the torso, the Tosai will not reach that trophy body size we are looking for. So what size are we looking for? When observing the best potential for size, we are looking for a bigger head in addition to that strong "shoulder" we discussed earlier. The Tosai will need a larger head. The larger head will be grown into, contingent on proper care and adequate feeding. The next area we will analyze is the tail section. We begin observing from the end of the dorsal fin to the top of the tail, we look at the length of this section. An observer should notice its length and width. Ideally, the observer should notice a long and wide tail section. This is a good indication that the Tosai will eventually become a strong swimmer, and their body will develop well. Lastly, we will look at the belly. A tip you should keep in mind is the Goldilocks rule. Make sure the koi's belly isn't too big or too small, it should be "just right." In conclusion for the body conformation, we are looking for a torpedo-shaped body from our Tosai when picking out. 
General Health:
One of the most important criteria that should be observed first (goes hand and hand with body conformation) is general health. Prior to purchasing a koi, observe how the fish is acting. Subtle cues such as swimming patterns will give you, the potential buyer, an indication of how the rest of the Tosai's health will be. If the pectoral fins are tucked in close to the body and swimming with only its back fin, this should be a concerning factor. Next, check to see if there are any external symptoms such as ich spots, fungal infections, blurry eyes, or cuts. In many cases, a dealer should have these koi separated and treated!
Pattern:
On to the next criteria for picking out a Tosai, the pattern! This is where most entry-level hobbyists begin their checklist. We must strongly advise clients to go through the body conformation checklist first, prior to looking at the pattern. The first part of recognizing patterns is understanding the type of koi. As you may have figured by now, all koi types develop differently. For example, a Tosai Sanke should have a very strong Beni (Red)  and a "duller" complexion to the Sumi (Black). Ideally, the Beni (Red) on the Sanke should have steps or separations that define the fish. The Sumi (Black) on the other hand should be viewed as the supporting cast to the Beni (Red). The Sumi (Black) should fill in the spots the Beni (Red) does not occupy. Lastly, the Shiruji (White Base) should be a milky white complexion. On the contrary, a Kujaku does not develop the same way. The progressions we look at in a Sanke should not be represented the same as a Kujaku. The reason is, color schemes are not the same and growth is not the same as well. When looking at the Tosai Kujaku's pattern,  look at the top of the head to make sure that the net pattern is even. Then, the colors should be laid out in a way that is distinguishable to the observer. As you can tell, different types of koi have different criteria when it comes to patterns. It is the buyer's responsibility to understand how the koi's patterns vary and develop. Going back to the general pattern checklist, we now move on to blemishes. As a koi enthusiast ready to purchase your Tosai, it is important to look for spots that don't belong. On a Yamabuki or Benigoi, it is important that a black spot or an orange spot should not be seen on the koi. This would be an imperfection to the koi that is called a "Shimi." A Shimi, which can occur to any koi, is a freckle that develops on the koi and tends to draw attention away from the beauty of the koi. More often than not, a shimi will develop later in a koi's lifetime if the hardness of the water is not checked and maintained. Another blemish you should keep your eyes out for is anything that stands out too much. These distractions will pull your attention away from the general beauty of the koi and should be reconsidered prior to purchasing.
Now that you have the general idea of selecting your next Tosai! Give it a try and happy shopping!