Question
dear brothers, i have an aquarium in my room and lately after one fish died i kept it there for a while. Does the presence of a dead creature (fish) affect the purity of my room? I have prayed salah during that state, are they ok?

Answer
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The death of the fish does not affect the purity of the room. Moreover, the dead fish is pure and not impure as the Prophet said: "There are two dead animals that are lawful for us (to eat): they are fish and locust, and there are two bloods that are lawful for us (to eat): they are the liver and the spleen." [Ahmad and Ibn Maajah]
Besides, Shaykh Ibn ‘Uthaymeen was asked: “Is the dead fish in a river, aquarium or pond pure?, and he answered: “The saying of the Prophet about performing ablution with sea water: ''Its water purifies, and its dead are lawful to eat.” [Abu Daawood and An-Nasaa'ee], includes all kinds of dead animals that live in water. So, any creature that only lives in water, if it is dead it is pure, this is what appears from the Hadeeth, whether this is in a pond, or in a river or in a spring, or anywhere else….”
Dear brother, we notice from you questions that you are afflicted with whispers about purity, so we advise you to fear Allah and avoid such whispers as it is a widespread evil. You should know that, in principle, all things are pure, and not impure. If someone opens the doors of whispers to himself, it may be difficult for him to close it, so you should fear Allah.
Allah Knows best.

Fatwa answered by: The Fatwa Center at Islamweb