I live in a city that has extremely soft tap water (total hardness is usually about 6 dH), but a friend in the country wants to set up a fully planted tank with tap water that has a total hardness of over 40 and a TDS of 440 ppm. I get the impression that the water in the UK is generally hard, and so I ask if there are any plants that he should do well with? And are there any plants he should stay away from? He wants to dose CO2 so I presume the pH can be brought down, but what should he expect? Cheers.