Well what I look for is nice conformation...To bad you dont have the amount of dealers we have here in Northern California in Hawaii. Well everything is a gamble, 50/50 they say, some more than others have the best of luck when it comes to picking tosai /jumbo tosai and growing them to sucess....
What I look for in tosai....my check list.
1. Check for any deformaties 1st and for most!!
2. Check for conformation...if the lines of both sides are equal you use the dorsal fin as a divider(imaginary line so to speak) to check this. Size of head, the distance of the eye from the end of the gill plate will most likely tell you the fish will grow big. Also the width of the nose too, the wider the nose the greater the overall apperance of the koi will be. Try to imagine the koi at 50 or 60 cm, you dont have to look to far in the future.
3. Skin quality if the head is a bit tinted then no good, slight chance it will stay that way. But general rule is that if the tint is consistant with the fins and body more that likely it will clean up.
4. Pattern and depth of color. Remember if the fish has to much sashi atleast 2 scales deep it will more than likely clean up giving you that sharp kiwa when it gets bigger and older, more that 2 or more scales deep probably stay that way. Pattern is to each his own of course, but maki plays a big part of it to so pick something that the maki is wrapped down enough to give you a uniform look to the pattern.
5. Finally breeder or bloodline, this is last because I think it is best to look for koi that gets your interest, not by breeder alone. Mind you even the best "Name Brand" breeder produces junk, so be aware of that. I ask about breeder after the I do the first part of my list. Then I make a decision, pass or purchase. The 2 P's, remember that. Don't get caught up in a buying spree because everyone else is buying. Until i do my check list with a koi then will I use the 2 P's.
Also, remember that no koi is alike, that's what makes this hobby cool. If there is a koi that strikes your fancy buy all means purchase it, but do your check list before you finally decide. It is always good to take a camera with you whenever you go koi shopping, I do. You can always take a pic(of course with the dealers permission first) of the koi you are interested in. Dewell, on it and see if the koi grows on you. I wouldn't take a pic of the koi until it passes the whole list first. Some dealers will hold fish if your seriously goin to buy, but never hold a fish for too long because the dealer loses chances to sell the fish to a customer who wants it now.
This is the list I go by, I am sure others have a different routine they have. Picking tosai/jumbo tosai for that matter is never a exact science. It's fun to still buy tosai after so many years in the hobby, I met newbies who say they aren't goin to waste their money on tosai. But where is the learning process? Sure we can all look at pics to give us a general idea, but everything is produced to see in person.
Last but not least, take someone with you who is alittle more experienced...or ask questions. I am sure you have met the Horimotos before they are a cool couple with alot of years in the hobby who know. They are easy to talk too and are very helpful.
Until the next post, Happy Koi Shopping.