1. Locate the flow control knob on the side of the filter.
2. Turn the knob clockwise to increase the flow, or counterclockwise to decrease the flow.
3. Make sure that the flow is not too strong for the fish in your tank.
4. You may need to adjust the flow periodically as the filter media becomes clogged.
Here are some additional tips for adjusting the flow on a Topfin 30 fish filter:
* If the flow is too strong, it can damage the fins of your fish.
* If the flow is too weak, it will not provide enough oxygen for your fish.
* Ideally, the water should be circulating evenly throughout the tank.
* You should be able to see a slight ripple on the surface of the water.
* If you have any questions about adjusting the flow on your Topfin 30 fish filter, you can contact the manufacturer for assistance.