I heard SE horribly nerfed fishing in towns a while back... is that true? Or was it just a rumor?
Anyway, if you're going for moat carp, I suggest Korroloka Tunnel, in the southwest corner of the map that has the NIN quest leeches on it (it's also the map with the zone to West altep (not East altep)). You can catch carp and sandfish there rather easily, and skillup on the sandfish until 50. There's also rusty caps, greatswords, and picks to be caught. There's a few monsters, but the strongest is a kraken, and if you bring a weapon and maybe some of your EXP gear with, you can kill them easily.
Not sure what rod to use there, though, as the patch changed rods a lot.