As long as they are properly done and the fish are not overly stressed (they will always be stressed a little... I mean, they are like total drama queens/kings!) then waterchanges are only helpful. I used to do 100 percent changes twice daily on my pond (400g) to keep the green water down in the texas sun (and i am not even stocked that full) and the fish never complained, not once :lol: Every morning I would wake up and open the drain, then come out after my shower (the drain is setup to leave 5 inches of water for the fish) and close the drain. We have an autotopoff so that new water is added when the water drops too low so when it is drained, the Auto Top Off constantly added new water so slowly all the water was new. Once I closed the drain it would fill with new water and viola, 100% change. I would do this in the morning and before bed...