The flow is strong, but he seems to like it and often surfs in it, but less often now that his fins are a bit heavier. When he was glass surfing all day long unless I covered the tank so that it was very dark and he went to sleep, and not eating, one of the pieces of advice I got was to switch up the current from the filter outflow. This gave him something to work against, and helped, but what really made a difference was putting frosted film on the back and sides so that he couldn't see a fish reflected in the glass, trying to get into his tank.