I have a question about tofu so please help =]?!

I have a question about tofu so please help =]?

i'm making dinner for myself tonight using half a block of tofu but i also need to save some for tuesday night when i'm making a tofu stir fry for myself and a friend.. if i use half of it today [saturday] will the other half be able to keep until tuesday which is like 3 days? and how do i store it until then? like should i freeze it? or just wrap it in plastic and stick it in the fridge? thanks for the help!

this is the first time i actually cook with tofu =]

2 days ago
EDIT + NEW QUESTION
so i just looked it up and it said to put it in a tupperware with fresh water changing it everyday.. but what constitutes as fresh water? drinking water or tap water? is it okay to use tap water or i should definitely use drinking water?

thanks!!

tap water is fine don't worry about it so much.