I don't remember the previous thread but I, probably, would have said this, then.
Check for any self-seeded plants that might have contaminated the water. Euphorbia, spurge, is one to look for as it is often spread by birds and is toxic to fish.
Best phone camera 2017
Stunning new film posters by Hattie Stewart, Joe Cruz & more
iPad Pro 10.5in (2017) review
28 astuces pour profiter au mieux de votre iPhone