I am new to the aquarium world, i have a 38 gallon tank, and my tank has started to cycle i believe, the water has started to go a yellowish color and smells like dog $#!7. it's started about 5 days ago, i did a 30% water change 3 days ago. i plan on doing a 50% water change tonight.and a 20% every three days till it clears up. but how long does it take for the bacteria to grow and balance out everything, i have the temperatur set to 25C and i have a airater in the tank. any help would be great.