Hello, im new to this site and aquariums all together, anyways i have a 50 gallon tank, and it was all good, till my girlfriend wanted pink gravel, so we emptied out the tank, placed new gravel, and the worst thing, we cleaned out the filter, so now i got 20 fish, all in there already, as i said im new, and the waters all cloudy and stinks because i dont have bacteria to break down the waste, what should i do? i added some nutrafin cycle and waste eliminator, also performed like a 40 pervent water change, the water stoopped stinking, but in 10 minutes it came back.What do i do?, i dont want all my fish to suffer and die.