Interconnect an 180 gal & 75 gal

[cagey]

I want to plumb the 180 and 75 together. I would like to supply the 75 from a fitting towards the bottom of the 180. the 75 is lower than the 180. Both on LFS stands. My problem is how to stop the 75 from emptying up to the 180 after a power failure. An air inlet will break the siphon down to the 75 but how to prime the line??? Neither tank is drilled. There currently is a 20 gal fuge under the 180.

Any Thoughts..

[metalhead]

I run two 90's on a common sump... I just tee'd the pump return line with a ball valve so I could regulate return flow between the two, works great. In your case though you'll need to keep your over-flows high enough in each tank so that the sump can handle whatever residual overflow hits it when the power goes off.

[cagey]

i solved my problem. The 20 refuge is now on a shelf behind the 180 about 2 inches taller and close enough for the U tube to fit. Pump same as before. I piped 2-1 1/4"
PVC lines from the 180 to the 75. and a mag drive sending back. calibrated to not overflow. Now in the 75 I have the other appurtenances.