Until its cycled, ie. until you get an ammonia, then nitrite, then nitrate spike and then ammonia and nitrite go to 0 again.how long do i have to wait before i put some fish in my new tank??
Which isn't cycling, it's letting the filter run for 12 hours in tap water and gaining no bacteria that'll stop your fish from dying becasue theres no ammonia to feed on.What I do is I put some salt on it then cycle the water for 12 hours.
leave it to cycle for a week or two weeks, to build up your aqauriums 'good' bacteria,
there is an article on here somewhere about cycling i suggest you read that aswell.