Hi! I need you you help. I am at my wits´ end. The problem is that my new tank of 15 litres has been cycling for 2 months already. I was even forced to change my old (it wasn´t actually old) filter for a new one, as it didn´t produce oxygen anymore. Now that I have the new filter in the tank, it naturally takes time to go another period of cycling through again (p.s. I took the old one out after I had installed the new one).
Does anyone have an idea, where did I go wrong? I have done small water changes every day, but I have never cleaned the gravel (it doesn´t seem (that) dirty, anyway).
p.s. I have only 1 big goldfish and few plastic plants in the tank.