If one has a fish tank it would seem that the the entire tank would have the status of a Bassis Ledavar Assur. That being said would one be allowed to remove the cover on Shabbat so that he can feed the fish or do we say the cover is also a Bassis along with the tank?
Aaron Massry, Brooklyn
You are correct that many Poskim consider the fish tank a Basis. However, one is obligated to feed the fish since they depend on us for their food, and therefore one is permitted to open the tank and feed them.
The reason for this is that there is a dispute between the Poskim regarding moving the fish tank itself. The Ketzos ha'Shulchan 121:4 is lenient because the fish tank is decorative and enhances the house, and similarly writes Rav Binyamin Zilber zt'l in Az Nidberu 5:36, and quoted in the name of Rav Shlomo Zalman Auerbach zt'l in Shemiras Shabbos k'Hilchasah 27:27, while Rav Moshe Feinstein zt'l in Igros Moshe OC 4:16 is more stringent, as is Rav Ovadyah Yosef in Yabi'a Omer 5:26. However, in our case there is an issue of Tza'ar Ba'alei Chayim which allows feeding the fish even l'Chatchilah and to rely on those who are more lenient regarding moving the fish tank. (See Piskei Teshuvos 308:54, note 448.)
Obviously, it would be advisable to leave food in the tank before Shabbos and not have to feed on Shabbos.
Yoel Domb