Interconnecting two Aquariums?

[SteveMM62Reef]

When I move my 65 Gallon, over next to my 120 Gallon, I want to connect the two sumps together. My Reasons for this is, one Sump has a Refuguim in the middle, and a Place for Filter Socks. The other one is a LifeReef. Each Aquarium will have it‘s own Return Pump(s). Drains will go to their corresponding sumps. Also will have their own Skimmers. Multiple Vacuum breaks, to control Syphoning. Also I’m going to do an Auto Water Change setup, that will change the water in two hours. Set a timer, and monitor, the Peristaltic Pumps. It’s getting a little tiring carrying buckets of water up the Steps, to Dump. Trying to figure out the size Interconnection Pipe, which will have a valve in it for servicing. 1 One inch drain on the 65 Gallon and 2 Two inch Drains on the 120 Gallon. The water level in the 120 Gallon Sump runs higher than the 65 Gallon Sump, so I may have to somehow reverse that. Any thoughts on this?

 

[DCR]

The levels in the sumps are going to equalize. Unless you create some cross-over flows between the two systems the flow through the equalizing line will be minimal (theoretically zero). You probably want to create some small cross-over flow from one of the return pumps to the other sump so that the water parameters in each system are the same since the auto water change and make-up will come from only one of the sumps.