Hi all,i change 50g every week and i use cold water through a hose pipe straight from the garden tap during summer i find this is no problem,During winter when the tap water is really cold i do add some hot water from the kettle after boiling of course, i would not advise using hot water from the tap because because it can contain high levels of total disolved solids (tds) and i have been doing this every week for ten months and i havent lost any fish at all,regards john