It's actually casual combination of two sentences. "Bokuwa nishikigoi ( ga suki desu). " and "(Nishikigoi no naka de) tokuni tancho to showa ga daisuki desu." So, Masa-san's translation sounds most accurate, I think:)

Boku wa nishikigoi no naka de toku ni Tanchou to Shouwa ga daisuki desu. Watashi wa nishikigoi no naka de toku ni Kumonryuu ga ichiban suki desu!

ぼくは にしきごい、とくに たんちょうとしょうわが だいすきです。 = "I love carp, especially Tancho and Showa." ただしい　にほんごですよ。 いみも はっきり わかります。 「は」は はなしことばでは、「わ」と はつおんしますが、かきことばでは「は(ha)」になります。

Boku wa nishikigoi, tokuni tancho to showa ga daisuki desu 僕は錦鯉、特に丹頂と昭和（三色）が大好きです。 It's neary correct. Of course make sence. It's diffucult sentence at Japanese. First,"nishikigoi"is carp.But tancho is "Kingyo" Showa(sanshoku) is great carp.

It makes perfect sense to me. He was asked which type of koi he likes. Therefore, he answered, "I (like) nishikigoi, especially tqncho and showa."