How big is the "bowl" (how many gallons ?)
How many fish, what are they and how big ?
Do you change all the water or just part of it
Do you clean the filter out at the same time ?
Is the tank in sunlight or in a very bright place ?
How much and how often do you feed ?
If you are having to change the water so often I reckon you must be overfeeding or something. The whole point of the filter, as im sure you know, is to clean the water for you. As suggested already, make sure its not in direct sunlight and also remember, goldfish will keep on eating as long as you keep feeding them. Only give them enough food to last a few minutes of feeding, they will then scour the stones for any lefovers..
Tank is average square size with 3 Fish in it. I think after speaking to people I am overfeeding them. Instructions on food say 3 times a day but I have now limited it to twice