understanding overflows

[Rsquared333]

I believe I have the concept of the overflow/sump/return pump system down. There is just one more thing I want make sure I am right about. That is that the gph rating doesn't give the actually gph of the overflow but the maximum it can handle. Therefore an overflow can run a any gph from zero to the gph it is rated. For example a 600 gph overflow will run at 450 gph if the return pump is a mag 7 at 4' (mag 7 has a flow of about 450 gph at 4'). This is correct, right?

 

[Rsquared333]

also has anyone notice a huge difference from getting a smoked or colored inner skimmer box? Is it really needed, does it help reduce algae growth, or is it just for aesthetic purposes?

 

[XXFirefighter]

yes on your gph question...
you can run a 600 gph overflow at 450gph...But it's overkill. WAY too big of a overflow...And if you go too big of a gap like a 600gph overflow with a 100gph return pump your gonna need a air siphon tube because the fitting will be too big and won't be able to keep the siphon...
And the smoked or black plastic does help...

 

[RMPD109]

I agree with xxfirefighter on both points. check the link for some more info.

http://www.melevsreef.com/what_sump.html

 

[Rsquared333]

thank you.