QCppg, I'm not sure why you're making
US seem like the dumb ignorant ones here, but could you stop? All the sarcasm and !!!'s are annoying. Thanks.
Anyway, if money is an obstacle then goldfish and koi are not for you. Koi get so big that they really need a pond starting off. If you wait, the fish will become stunted. I dont know how you expect the Koi to reach 8" when hes only in a 20 gallon tank with multiple other fish too.
And definately get those water readings. Unless you've done those readings, you really have no clue if this tank has cycled or not. Ammonia and Nitrites should be at zero if cycled... and nitrates should be under 20-30 ppm.