my blenny took his first ride today.
 

well, after not being able to find my blenny for a day, I looked in the sump and thats where he appeared!!! I dont want him to rid down the overflow again, so is there anyway I can block it off for fish without reducing any flow? thanks.

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.

yup their is teeth there....they is about a 1cm gap....so i supposed i could try to reduce that.

Try gutter gaurd.

... or nylon window screen.

I made 2 little flaps for a piece of eggcrate to fit on.. hasn't failed to this day..

thanks for the ideas

I use eggcrate shaped to fit my curved overflow; with some fiberglass window screening sewn onto it.

I use a medium pond filter that's placed in front of the bulkhead inside the overflow box. It's big enough that it won't get sucked into the hole and also course enough that it does not impeed flow rate. I prefer this method for my setup, that way if a fish does manage to fly over the overflow, it will remain alive in the bottom of the overflow until I can "fish" it out.

cheers, Rich