I saw this video on Toxic gas in your Aquarium and found it very informative as I do all his video's as he is a Micro Biologist and Fish Nerd Enthusiast. ;D
https://www.youtube.com/watch?v=ZAI7oV7i4Iw&t=6s (https://www.youtube.com/watch?v=ZAI7oV7i4Iw&t=6s)