From everything I tried, I was only able to pause it while it sleeps, but that's it. Even then the water temp drops and could drop to a dangerous temperature.
Well, I hope since this is the third day, it'll have the 'new tank' screen and I can leave it on that. You said it changes the morning of the third day, right? If it doesn't change today, it'll probably change tomorrow, so maybe someone could take care of it 'til then... my sister's at school and my mom doesn't have a clue in the world of how to work any virtual pets,but I guess I could teach her until the change....Oh,well.Thanks for trying.
Edit-The changing screen showed,but when I got back on the fourth day and pressed C to make her become an adult, it showed me a picture that meant 'ran away because of dirty water'