My only beef with the common names is simply the vagueness and the fact that names are often shared among species and that can cause confusion with getting proper care for that species.
If they were consistent across the board it would be no issue for me.
I'm also the sort of person that likes to know exactly what I've got when I keep something, so a vague idea isn't enough for my curiosity. So for my personal preference, I like the exact names. Some species I keep also don't have common names, such as my bario forestii. Most in the hobby would just throw them under the "red eye tetra" label and be done with it, but they're a legit separate species from what's supposed to be "red eye tetras" and have morphological differences and even size differences between it's lookalikes. The size factor can make or break your tank size choice for it, imo, so to me it's beneficial to know exact. Does it 100% matter at the end of the day? Not particularly, as care conditions are similar.
But if someone were to ask, could they keep red eyes in a 29g tank or such, it would depend. True red eyes, bario sanctaefilomenae, I'd say no because they get a good size and have a bad attitude so would be better off in a 40g+. But bario forestii is smaller and could be kept in a 29g. And, to most folks they look nearly identical. They have to be told apart mostly by lateral line and scale counts.
But, I'm not gonna look down on another person who uses the common names either, as long as they know what they have.
And then we have another issue with confusing names--> hybrids.
Bedotia madagascarensis, the madagascar rainbowfish. It's so often mislabeled as Bedotia geayi, and there's speculation that they've been interbred in the early days. So what's in the hobby is more often madagascarensis or mixed fish. Neither are really collected from the wild anymore, but there is confusing genetic makeup of these fish. The same deal is for common bristlenose plecos, ancistrus cf cirrhosis. No one is sure what the actual fish is, because it's been muddled up so much in the hobby by people who don't particularly care.
So sometimes, it's good to err on the side of caution and know what you've got. Others, in terms of care, it doesn't really matter except personal preference.
If they were consistent across the board it would be no issue for me.
I'm also the sort of person that likes to know exactly what I've got when I keep something, so a vague idea isn't enough for my curiosity. So for my personal preference, I like the exact names. Some species I keep also don't have common names, such as my bario forestii. Most in the hobby would just throw them under the "red eye tetra" label and be done with it, but they're a legit separate species from what's supposed to be "red eye tetras" and have morphological differences and even size differences between it's lookalikes. The size factor can make or break your tank size choice for it, imo, so to me it's beneficial to know exact. Does it 100% matter at the end of the day? Not particularly, as care conditions are similar.
But if someone were to ask, could they keep red eyes in a 29g tank or such, it would depend. True red eyes, bario sanctaefilomenae, I'd say no because they get a good size and have a bad attitude so would be better off in a 40g+. But bario forestii is smaller and could be kept in a 29g. And, to most folks they look nearly identical. They have to be told apart mostly by lateral line and scale counts.
But, I'm not gonna look down on another person who uses the common names either, as long as they know what they have.
And then we have another issue with confusing names--> hybrids.
Bedotia madagascarensis, the madagascar rainbowfish. It's so often mislabeled as Bedotia geayi, and there's speculation that they've been interbred in the early days. So what's in the hobby is more often madagascarensis or mixed fish. Neither are really collected from the wild anymore, but there is confusing genetic makeup of these fish. The same deal is for common bristlenose plecos, ancistrus cf cirrhosis. No one is sure what the actual fish is, because it's been muddled up so much in the hobby by people who don't particularly care.
So sometimes, it's good to err on the side of caution and know what you've got. Others, in terms of care, it doesn't really matter except personal preference.
) and simply called them Dennison barbs, or just Dennies, and people knew what I was talking about. 
