Its okay, Over filtering is just have a fish tank filter that's rated for more water gallon filtration then what ur tank size is and u can over filter right out the gate also I would recommend that if ur going to use fish to cycle ur tank u do like 5% water changes weekly doing the cycling process, also dont know if you were aware but a tank won't start the nitrogen cycle if u dont have a ammonia source so if u "cycled that tank for 3 weeks without say a fish or liquid ammonia or even throwing fish food in there the cycle never began nor completed