Answered by Shaykh Faraz Rabbani
Question: Is it permissible to keep pets, such as fish in an aquarium or birds?
Answer: In the Name of Allah, Most Merciful
I pray that this finds you well, and in the best of health and spirits.
In terms of permissibility, it is permitted to keep pets if one is sure that one will give them their rights in terms of proper feeding, cleanliness, dignity, and care. The same thing would apply to keeping fish in an aquarium.
If there is any fear that proper care would not be taken, then it would be best not to keep a pet or aquarium, as it is sinful to be cruel or oppressive towards animals. [Nahlawi, al-Durar al-Mubaha]
The Messenger of Allah (peace and blessings be upon him) mentioned that, “A woman entered Hell because of a cat which she tied up and neither fed nor let loose to feed on her own.” [Bukhari and Muslim]
And Allah alone gives success.