Note that syphoning can only move water to a lower elevation. It can go over an obstacle (literally uphill) to do it, but the water level in the receiving vessel -must- be lower than the donating vessel.
So you could use a syphon to go from a to b, (b is lower), and b to c (which is lower than b), but you can't use a syphon to go from c to a. Now you have to oppose gravity and use a pump to gain the elevation back
'While a simple siphon cannot output liquid at a level higher than the source reservoir, a more complicated device utilizing an airtight chamber at the crest and a system of automatic valves, may discharge liquid on an ongoing basis, at a level higher than the source reservoir, without outside pumping energy being added. It can accomplish this despite what initially appears to be a violation of conservation of energy because it can take advantage of the energy of a large volume of liquid dropping some distance, to raise and discharge a small volume of liquid above the source reservoir. Thus it might be said to "require" a large quantity of falling liquid to power the dispensing of a small quantity. Such a system typically operates in a cyclical or start/stop but ongoing and self-powered manner.'
Samuel Morton wrote:Ah so would the slight increase in atmospheric pressure between C and A would prevent the siphoning work to move the water say from the fish tank to the grow bed?
Correct, the water level is usually lower in the grow bed, compared to the level of water in the fish tank. Also, the potential energy difference affects it. The higher water has more potential energy than the lower one.
It is the height difference that drives the syphon, but it is expressed or translated via the air pressure. Syphons don't work in a vacuum.
Mr. Morton points out an interesting device that works similarly to a hydraulic ram. It is not a ram pump, but it is similar in that it uses part of the kinetic energy released by the water running downhill, to produce a
small container of water at a higher elevation than the original water source.
The main drawback being only a small or tiny percentage of the water moved, ends up at the higher elevation.
This is sometimes referred to as volumetric efficiency. Every installation is different, but let's say you have a 2 meter head (difference in height between the inlet and the outlet of the ram pump).
A good ram pump will provide 14% volumetric efficiency with good input flow rates. Meaning 100 liters of water, moving at a good clip, going through the ram pump, will produce 14 liters of water at the higher reservoir.
Most aquaculture setups would have a head measured in inches, not in meters, and fairly slow flow rates, resulting in much lower potential and kinetic energy available. So you -might- be able to raise 5% of