A quick comparison to the two sides of Fisheye: anime and manga

Reign of Terror
Anime: 22 episodes (SuperS 128-149)
Manga: 1 act (Volume 12, Act 35)

Birth
Anime: Who actually created him from the fish is not clear. It was probably Zirconia
Manga: Created by Palla-Palla

Death (Part 1)
Anime: One of the Amazoness Quartet's lemures does him in...
Manga: Sailormoon, Sailormercury and Sailorchibimoon do him in...

Death (Part 2)
Anime: ...but Pegasus brings him back, along with the rest of the Amazon Trio. They are taken to Illusion to live in safety.
Manga: ...and he stays dead.

Soul-Searching
Anime: Near the end of his life, Fisheye begins to realize the value of dreams...especially since he had finally found something (Mamoru) worth dreaming of. His character definitely changes as he learns what he doesn't have, what he could possibly never have, and exactly what evil has been controlling him. The very moment where he crosses over from good to evil? When he fixes Usagi's dream mirror, of course
Manga: Forget it. This incarnation of Fisheye was born purely evil and died the same way

Victims Attacked
Anime: 7 of them: Kitakata, Yoshiki Usui, Robert, Yamagishi, Makoto, Mamoru, and Chibiusa. 8 if you want to count the aborted attempt to get Tiger-Eye's dream mirror
Manga: 1: Ami

Getting the Job Done
Anime: Fisheye plans extensively for his victims; he goes to great lengths to seduce them. Often, he tries to find out the victim's interests and infiltrate through that channel (dancer, fashion model, fairy *g*) first, before resorting to violence. The two female victims, Makoto and Chibiusa, were unplanned so he took by direct force
Manga: One victim, one tactic. Learning that Ami has an affinity for water, Fisheye passed himself off as a cute fish which Ami was drawn to and ended up purchasing...I guess you could call that a seduction, of sorts

Sexuality
Anime: Fisheye loves men...REALLY loves men ;)
Manga: Fisheye's sexuality in the manga is never clearly defined. Neither is his gender...though I guess mentally I've always dubbed manga Fisheye a "he", especially since he was putting the moves on Ami

Power-ups (not of Fisheye)
Anime: In episode 143, while Fisheye is attempting to throw knives at Sailormoon and Sailorchibimoon, the four Inner Senshi confront Pegasus. Pegasus implores the girls to trust in him, and are powered up to their Super forms
Manga: Ami becomes Supersailormercury and discovers the wicked power of the Mercury Harp: Mercury Aqua Rhapsody

Overall
Anime: Although starting off evil, Fisheye begins to develop layers to his personality that he as the season progresses. He's got a vain side, he's man-crazy, he gives a little of his heart to each victim (shades of Mimete here), he's got a sense of humor, and he's smart...albeit ditzy. He also learns the painful lesson that he is not human, and he has to make many tough choices in his life for him to achieve his goal of having his own dreams
Manga: Fisheye does not live long enough to develop a distinct personality. He is your basic MotD (monster of the day) sent out by Palla-Palla, and like all MotDs meets a violent and fatal end