Weirs and external overflow boxes

[Megalodon]

I'm putting two external overflow boxes on my 90-gallon tank.

I have already ordered the glass. They will be 25cm deep, 20 cm wide, and 11cm thick. I'm thinking now that they should be wider but not as deep, but I guess it's too late now. Do you think it really matters that much?

Also, for cutting the weir, this is what's really troubling me. How do I cut it? How deep should it be? Should it cut into the upper black plastic rim or be just below it? Should it have teeth or just be wide open?

Thank you in advance for helping out here.

:bum:

[das75]

I would just go straight (no teeth) as seems way easier.

Seen this 120g tank running (picture below, was Skimmin's on Canreef). The weir was just a straight cut with eggcrating. Seemed was cut a little low as even with 2000gph the edge of the water was noticed as the overall height in the tank was only ~1/4" above top of the weir.

You can work from here (http://reefcentral.com/calc/drain.php) to get on idea of weir length (linear overflow size). The calculator seems to give a height of about 1/4" about weir.

Another calculator is here (http://www.reefs.org/library/downloads/) just make the number of opening as 2 and you can find height above for different flow.


http://i193.photobucket.com/albums/z89/crystalzbucket/IMG_0806.jpg