I mixed it in gradually when spot cleaning so by the time I did a cage clean and replaced half the substrate most of it was Fitch and the time after that I went fully over. Again it probably depends on the hamster a bit as to how gradually you do it, but it could be an idea not to change all the substrate in one go at first. I found when I had the Fitch mixed with shavings our Syrian liked picking out the bits of Fitch and taking them to his nest - it's nice and soft for their nests as well - but I still put out torn up strips of toilet paper for nesting as it holds the nest together better
