Another spot you can add is the little pond behind the Warden/Fisherman's houses in Fuchsia.
When using the Super Rod, you generally get Goldeens, Seakings and Gyarados for +1, +2, +2 ATK EVs respectively.
It's mostly just those three, with level ranges of around 17~30 between the three Pokemon. Can't remember whether the levels are fully accurate, was training there around a week ago.
Edit: Just checked, these are the ranges
Goldeen: 15-25 (40%)
Seaking: 20-30 (40%)
Gyarados: 15-25 (15%)
Given said levels, it's also a decent place for exp if one really wants that, but if people are trying to keep low, still better to stick to Paras.
- I did a bit of a race though with a friend, I had 0 ATK EVs and he had around 25~50 I think at the time. After some time he had already reached around 90 but I had surpassed him and gone up to 110.
Sometimes you might randomly snag a Psyduck or Slowpoke though at 5% chance each, both ranged at Lvls 15-35.