The problem with eating too much fish is mercury. I'm not an expert on how much is too much but at a certain point you can get mercury poisoning by eating too much, too often. A quick google search told me flounder is low in mercury compared to other types.
"Getting solid information is easier than ever. Getting misinformation is even easier." - Kaplods
Maintaining for two years and I eat whatever I want - just not however much I want. Details here.