Colorful pond fish (3)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">colorful pond fish</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for koi that I've seen before include "Japanese fish" , "Sort of carp" , "Carp; sounds like shy" , "sort of fish" , "Kind of decorative carp" .)