I "Used" to have a 35g tank with 7 Kuhli Loach, 8 Harlequins, 1 Male Dwarf Gourami, and 10 Neons
All fine until 3 months later all the neons started to died
The water PH is 6,5
Ammonia 0
Nitrite 0
But for some reason others are still alive until i give the tank to my neighbor