[superbrat]

I need to know how to control the tank water level. I have a 120 gal with two overflows. Each overflow has a 1.5 inch pipe or tube where the water drops down to the sump. Each pipe or tube, is a tube within a tube, and the length of the tube can be changed by moving the outer tube up or down. I remember something about adjusting the height of the tubes up or down but when I do the level in the tank does not change.

Can someone explain how to get the water level down?

[BLKBRDTA]

Welcome to Reef Builders John! Do your overflow boxes raise and lower as well or just your siphon tubes? Raising the tubes makes it harder for water to continue traveling up, increasing the water level in the display. Lowering the tubes makes it easier for water to flow upwards and the level in the tank lowers. Adjustable overflows also help with maintaining a constant level in the display. Try adjusting them once again and wait a few minutes to see if the level changes. If not then you may have an air pocket that can sometime collect at the top of U-tubes. Fixing this is easy, just stick airline tubing (or even a straw) inside up to the top and start the siphon over again.

[map95003]

are these built in overflows? sounds like they are, you could try lowering the stand pipes, however you have to balance your overflow rate and your return rate. Your overflow rates are restricted by overflow holes in your tank. If your return pump is pushing more than the overflows can handle you may need to add a valve on your return pump(s) line and crank it back a bit.

[superbrat]

Thanks to all! I have built in overflows and cannot move them.

I did move the pipes down a little and seems to be better. Also cleaned the inlet to the overflow box which seem to help also.
Thanks again for the response!