VERY good advice. I chaged my Rosea's subs on Friday or Saturday due to a bad smell and she has only statred settling again now. I only realised after reading this what effect it could have. I will now be doing my regular cleaning far more thorough.Changing substrate that often leads to T stress. T's in their natural habitat can live in the same undalterated 5 square feet for 30 years ! Listen to people like Talkenlate04. Unless you have something that threatens your T ( molds or mites ) leave them be. Spot cleaning is all you need to do on a regular basis.