Topping off
- Thread starter MollyBreeder
- Start date
water change is to remove waste from a tank. water evaporating leaves all the dirty stuff in the water still.
the tap water contains trace amounts if minerals and metals, and thefish add in nitrates, solid waste, and assorted hormones and other biological extras. when the water evaporates, those things are all left behind, but the pure water evaporates away. when you add in more water without taking any out, all of those things build up and become concentrated, making the tank water less than ideal and bringing it further away from the make-up of the tap water. do nothing but 'top-off' for too long and your tank will get "Old Tank Syndrome", which means the fish are so used to living in stale, bad conditions that doing a big water change can actually hurt them, because the tank and tap vary so much. kinda like giving a big bowl of food to a starving dog - even though it is theoretically good, the shock of it can be too much for neglected fish to handle.