First, it should be noted that these are in fact two different series, but for some reason IMDb has them listed on as one. They're both based on manga stories by the same person, Rumiko Takahashi, and they're both released by Geneon and thus feature many of the same English dub voice actors (I don't know about the Japanese ones,) but that's about where the similarities end. There is the "MERMAID FORREST" T.V. series, which is one (fairly) long-running series that tells an ongoing story. (Although both the Mermaid manga and the anime leave a few loose ends hanging that never get resolved, for example that little immortal boy never gets killed, the one thing that left me dissatisfied with it.) Then there is "RUMIKO TAKAHASHI ANTHOLOGY", which is a series of self-contained stories, each containing it's own situation and set of characters.
Even the tone of the two shows is very different. The Mermaid series is another fantasy by Takahashi (though a much darker one,) while the stories in "Anthology" tend to be more realistic, with a few exceptions. (For example, one story has an actual "gremlin" which only one woman can see.) More importantly, though, "Mermaid Forrest" is a horror story (and often times a pretty graphic one,) while the stories in "Anthology" are much more light-hearted, though they do sometimes venture into the realm of suspense. (In one story a woman begins to suspect her next-door-neighbor may have murdered her mother-in-law, while in another tale a girl becomes afraid that her family's latest outing is in fact a planned suicide.) Each show is well-worth seeing (though again Mermaid Forrest does leave you feeling like you haven't seen the complete ending,) however it must be stressed that again they are in fact two different shows. Trying to lump them together is like trying to take two different shows like "Tales From The Crypt" and "The Cosbys" and then trying to say they're both the same show.
Even the tone of the two shows is very different. The Mermaid series is another fantasy by Takahashi (though a much darker one,) while the stories in "Anthology" tend to be more realistic, with a few exceptions. (For example, one story has an actual "gremlin" which only one woman can see.) More importantly, though, "Mermaid Forrest" is a horror story (and often times a pretty graphic one,) while the stories in "Anthology" are much more light-hearted, though they do sometimes venture into the realm of suspense. (In one story a woman begins to suspect her next-door-neighbor may have murdered her mother-in-law, while in another tale a girl becomes afraid that her family's latest outing is in fact a planned suicide.) Each show is well-worth seeing (though again Mermaid Forrest does leave you feeling like you haven't seen the complete ending,) however it must be stressed that again they are in fact two different shows. Trying to lump them together is like trying to take two different shows like "Tales From The Crypt" and "The Cosbys" and then trying to say they're both the same show.