They are all one system so I only chage water from one location and I spill enough water on the floor each week I end-up changing about 5% a week.
Everything dumps into the 150 rubbermaid tub. My pump off water volumn is still to great for the 150
sump so I loose a bit on the basement floor when the pumps shut off(unless I close ball valves).
I was having problems with my dehumidifier tripping a surge protector, which would shut my return pump off. Also the Aqua-C
Skimmer like to over flow when it gets to much pressure.
I love having the sysem plumbed together. I think the advatages are greater than the disadvantages.
Advantages
Testing , water changes, heating/cooling, skimming,
Ca reactor, carbon, and PhosBan are all done from one location. I still feed and and Phyto to each tank.
Disadvantages
Ask Rob. Something bad happens in one tank it happens in all unless your home and stop it from spreading.