I'm thinking of doing a herbie style overflow, external to the 20L. Using a maxi-jet 1200 for the sump return. I used the RC calculator but it kept giving me 0 flow and I know other people use the maxijet 1200.

How big do my 3 bulkheads need to be? Is 3/4" too big?

3/4" can only handle 300gph; so no, I don't think that's too big.

linky to most ? about drains.
http://www.nano-reef.com/forums/index.php?showtopic=69372

heres a really good 20l thread, its half way in but the part you'll care about.
http://www.nano-reef.com/forums/index.php?...2480&st=100


as for drain size, simple awnser is...............................................

go with 1" and never worry about it again. if your doing a herbie style then there will be a valve to control it any way. with a 1" you can up the pump size later to most anything you'll want.

Looks like you can plan on about half of this. However, it might still work with the Maxi-Jet as head pressure will limit its flow, but as bitts suggested, 1" bulkheads would be better. 3/4" is minimum at best.

turn your way back machine to the old days of wet.
http://www.nano-reef.com/forums/index.php?...=19572&st=0

and my fav calculator, shows how it actualy works.
http://www.grow.arizona.edu/Grow--GrowReso...?ResourceId=188


Edit
Also by exo did you mean. an exo overflow box or just the bulkheads coming out the back of the tank.

Ok thanks!


Thanks for the links and info



Alright, I was hoping to keep the space needed behind the tank to a minimum, but 1" sounds safer.



External overflow box. I cut a notch in the glass and I'm going to glue a box on the back. The bulkheads will be in the box. So I was hoping that I could keep the size of the box smaller, but 1" will do.


Thanks for all the answers and reading materials!

Yup, definitely going to do 1" bulkheads. Thanks guys!

exo = awesomeness.

make sure to have the corners tou cut into the tank rounded or the tank will eventualy crack.
how wide is the wier, the wider you can make it the lower the flow at any one point. this will improve many aspects but mostly keep things from being sucked over the wier. this was the improvement most people say they would do to there exo.

I think mine is about 1". I'll double check later. It's rounded, not perfect but it's rounded.

should be good enough. keep us updated.

Got the bulkheads today. I'm going to try to cut the glass and silicone the external overflow on today or tomorrow.

if your useing a dremel the bit your gonig to need is a 562 tile cutting bit.

also cut a jig and use one of those atatchments that allow you to keep it at the right angle.
http://www.dremel.com/en-us/AttachmentsAnd...il.aspx?pid=566
while cutting mine without it the dremel bucked a couple times scratching the glass.

Thanks I have a diamond bit that worked well for cutting the slot in my tank. I'm hoping it will cut the holes ok too. If not I'll check out that bit.

pics!