DIY sump and overflow

[mattywatty]

guys i have a question,
i've been building my sump and overflow and am having trouble getting the overflow to siphon sufficient water. i did some calculations and comparison to similar models on the internet, it is a J-tube style. anyway anyway, i build and tested the overflow using freshwater first, naturally, but when i hook it up to my tank (saltwater) it doesnt flow enough. i cant think of any major chemical differences between FW and SW that could affect how much water flows through the tube. anybody have any thoughts?

 

[saltguy21]

difference in height during tests?

 

[gobie]

i myself hated j tubes so i had mine drilled it was the bes thing i ever did. i wouldnt ever go back