I’m finding there is no magic answer. Some people get it done in 3 weeks (reportedly). I have a 20 gallon long that hasn’t made a single change in readings in 2 weeks and I’m being told this is normal. 2 months is typical +/- weeks.HDavid said:I’m new to having a large tank and was just curious how long a 120 gallon tank takes to cycle and how long it will stay cloudy for. Any help is appreciated.