here are the pics, i want to tie the 20 gallon in but i don't know how to keep the water levels the same, i don't want a sump to go and end up with saltwater all over my floor.
here are the pics, i want to tie the 20 gallon in but i don't know how to keep the water levels the same, i don't want a sump to go and end up with saltwater all over my floor.
You can make the return go to the 20, over the side. Drill a hole at the top side of the 20 and overflow thru a pipe to the main tank. I did it, worked fine. Be sure to use a strainer anywhere a snail can get is, cause they will!
Make sure that the baffles are low enough, that if you shut off the pump, it will not over flow until the overflow stops. Keep the water level in it low, and you'll be fine.
I would definatley have the refugium under the main tank, but even if i did have it above the main tank wouldn't i want the water going through the refugium to be slow moving so i wouldn't want the return from my sump to hit the refugium
When I did it I split the return, so not all of the water went thru the fuge. If you don't want the fuge to be above the main tank you can reverse the setup; have the overflow split so part of it goes to the refugium. That then overflows to the main sump. I misunderstood your use of the word "above"