Good morning from sunny Port Talbot...!
The water in South Wales is generally very soft, mainly due to the miles and miles of rock and mountains that cascade behind us up into mid-Wales.
I have spoke with quite a few fish store workers around our area and alot of them say the same. What you really need to do is get a water hardness kit..this will prove whether or not Roath and Cardiff in general is the same. Soft water can have an effect on your PH during your cycling, it would 'crash' my PH during both fishless cycles i have done..but should it do that then we can get to that should/when it happens.
Diolch An Fawr,
Terry.