my blenny took his first ride today.

[ron101]

Do you have teeth on your overflow box?

If not: you can make some out of plexi, lower the water in your tank and run it sumpless for 24 hours, and silicone some in. This may cause the equilibrium water level in your tank to rise due to the added restriction if your pump output remains constant.

If so: Are they too far apart? Can you make them smaller and narrower?

I can't think of any modification that theoretically wouldn't cause some sort of restriction but some may be negligeable.