on needing to make the overflow out of glass...
i designed an overflow chamber on my 10 gallon and it was secured into place with only silicone and held perfectly fine. i have an mp10 on the tank and even opened at full throttle this thing does not even budge.
something i figured out staring at this thing for hours... even a slightly lower water level in the overflow area will cause the water in the aquarium to push against it from higher pressure? it is being held in place not only by the silicone but the water pressure in the aquarium.
some food for thought if you dont feel like building two overflow chambers together in place of one. our nanos have a very limited supply of real estate
every 1/8 inch counts