My siphon line to my sump is 12" higher than display water line. How can this work? Does the water have to go to a central tank them pumped to sump which is 20 ft away in another room. This was my only plumbing option because my basement is finished.
Well I would certainly look for another option, and get away from things that require a little engineering know-how to accomplish. In most cases, save for large tanks, a basement sump 20 foot away is really getting carried away. You will find a standard under-tank sump, and plumbing, a lot less complicated with less trouble potential. Just because you got it, does not mean you have to use it...
That said, 12" lift on a siphon is not really a problem, provided the outlet is lower than the aquarium water level. Since the maximum lift for a siphon is ~34' (based on atmospheric pressure at sea level; it lowers with elevation rise; practical limit is ~20') before the water hits its vapor pressure, both ends should be submerged. It is not quite that simple though.
The downside is, it will most likely have to be primed to get it started, and it will not just self restart, requiring manual priming each time. Not exactly a plus for aquariums, whereas for a dam it has a place. Once it is running at siphon (air purged out) it should not break, till the power goes out, or you need to shut it off.
As far as intermediate pumps go, I would want an engineer handy, because even with a very small imbalance, it is flood city, and it damages your home, rather than overflows a drainage channel.
I would not do this, nor would I recommend it, but then I am about things that work the first time, not "it will work if" sort of things...stick with a single under-tank sump.
