Hi! I'm flying abroad on Tuesday and I got someone to feed my betta,but now I realized he will need a water change as I'm going for a week. There are many risks in letting someone (my sister) that doesn't have any fish do a water change, because she could do something wrong innocently, like forget something or check the water temperature wrong or whatever.. So my question is, can a betta manage to hold without one water change without becoming sick in any way? Felix lives in a 12-13 possibly 13.5 liter tank. I have a sponge filter inside, but without the air stream going because even on the lowest level it seemed to interrupt him. I used to do 1 100% and 1 50% every week, but now I almost always do 1 100% (instead of two) and 3 50% (instead of 2) in two weeks.
To sum everything up in case I'm not clear - I'm going abroad for a week and am wondering what to do with the water changes. Should I let someone who knows nothing on tank maintenance change the water and take the risk of something happening or will ny betta Felix be fine without one 50% water change?