Still won't help if the pH is too different. Complete water changes are best avoided IMO. 50% is the most I'll do and that's only if somthing is seriously out of wack in the tank ie filter malfunction etc. You should really pick up that piebald barra eric, would be quite a showpiece and for that price...Eric A;3544212; said:I wait an hour minimum when I do a complete water change with cold water. Thats what it reccomends on the heater pacage, and thats the time it takes my thermometer to show the right temp.