So we are looking after some coldwater fish in a 80 litre tank with filter .
The problem is they are all dieing and we don't know what to do . 8 have .died over the last 2/ 3 days
They are fed x1 / day the normal food .
We took a sample of water to pets at home who do testing for free , and they said the water is text book perfect - so what is it and what can we do ?
Any usefull help appreciated and rep given