Re: Are Frequent Water Changes Harmful ? Because I have discus I do a 50% water change weekly. If I have to miss a week I notice that the fish are not as active and do a lot more hiding. The plants seem to tolerate this ok. At my store we tell customers to do 20-30% once a week. When ever there is water quality issues and the customer is honest we will find that they are not doing the water changes. An other reason to do regular water changes is that a lot of fish will secrete a hormone that keeps everone but the largest fish from growing. There is one gal who has her tanks on a schedule that changes water daily. I find that she has more problems with this system than I do with a once a week schedule. |