Read in a thread here,that when doing water changes, that you can turn off your filters, add dechlor to the tank, then add water directly to tank without pretreating. I am a pretty lazy guy and jumped at the chance to cut a corner. Also my tank is 300G and pretreating and pumping it in is a 3 hour job compared to 10 minutes with a hose. Anyway, I used this procedure 2 weeks ago and had no problems. Did it again last night 2/3 WC, I just got home from work, and my tank is starting to get cloudy. Tested water, nitrates < 20, nitrite=0, nitrate .25 . Somehow I must have messed up the BB. Only thing I can think of is last time I filled it alot slower, this time I turned the hose full blast and filled 2/3 of the tank in about 10 minutes. I guess this is what I get for being lazy. I will monitor water daily and do water changes as required. What should I expect? Will this take an entire month to clear up, or should it be a mini cycle? I am pretty disappointed, thought I would be able to get in alot more WC's with this technique, but guess not.