I have a 75gallon , 20gallon and a 29 gallon cycling. They have alota feeders, i would say like 20 or more in each. The water on the 75gallon is starting to get a lil yellow tint, so i wanted to do a water change on the tanks. Is it safe to do a water change even though the tank is cycling? and if i cant do a water change what should i do?