I would name him:
"The Eliminator"
"Rainbow Death Squad"
"Pookarific"
"Partly Cloudy" (the yellow is the sun, the light colour is a cloud and the blue is the sky}
"Skyy" (like the sky but with 2y's to make him seem cooler"
"Sunshine"
"Maxwell"
"Chiquita"
"Halo-Halo"
"Langka Sundae"
"Fishington"
"Fishly"
"Fishums"
I can go on and on. i kinda name things a bit weird. I just look at a creature and name it whatever comes to mind or observe its personality. Goodluck with the Fish names! I don't fancy giving animals people names.