i hope the best will come out of the family meeting. i must admit i went over the line a bit myself when getting a 5th betta. i didnt have much space myself for a spare tank but ended up puting one on my dining table.
i would agree to look for a alternative spot in your room to put the tank. a shelf worth of books or something similar in storage space is worth it to put the betta in a safe place in your room. a space on the floor is most likely better than an area where your sister can access to feed the fish. it sucks that you are put in such a condition regardless of your families view of fish. just try to get through this situation and make the best of it.
Kigurumi (F) yellow PK 7/4/13, Kurama VT 9/8/13, Zeydalus Salamander EE PK 21/3/14, Ryuk turquoise dragon DeT 8/5/14----Crested Gecko (8ths old) Sven Cal 27/12/11,
RIP: Osiris copper DT, Nel blue VT, Nelliel turquoise grizzle DT, Zaku red cambo, Blitzkreig Pineapple CT, Halloween orange chocolate DeT, Grimmjow, turquoise green CT