I have not had plaice before, but salsa does go great certain fish. When I make salsa I use: tomatoes, red onion (yellow onion will work though), chili pepper (as hot as you want it), garlic, olive oil, lime juice, cilantro, salt and pepper. I do not know exact ammounts, because I just make it to taste. As for corriander in salsa, no idea what it tastes like. There is only one way to find out though and that is try it. Just make a little extra of the salsa and put some corriander in with the extra. That way if it does not taste good, you still have great salsa to use and if it does taste good you can add it to the rest.