The good news regarding the maintenance of a copper fountain, is that there is none. Copper will naturally oxidise and this layer of Verdi-Gris will actually prevent further degradation of the metal by forming a barrier against the action of the elements.
Verdi-Gris is the green build up you see on copper roofs and can take many decades to build up. We have had copper fountains outside now since 1999 and still only small tinges of green have appeared. This continued patination of the surface adds character and beauty the copper, which makes them all the more special as the years pass by.
I have been asked about pipes freezing and bursting in Winter. This is not a problem, as when the pump is turned off in the Winter months, the water simply drains back into the pond, leaving the pipes empty. If the pump is left on during a freeze then the water from the bottom of the reservoir (which should never freeze if deep enough) will keep the pipes clear. If in any doubt then turn the pump off and if you have a shallow reservoir or one above ground, remove and drain the pump during Winter to protect it.
Copper pipes are safe for domestic drinking water, as copper is not generally soluble in water. Take care when using chemical additives in a pond though, as these may dissolve the oxide build up of the copper, which is not environmentally friendly and are best avoided in ponds where wildlife & fish are likely to be. Advice should be sought from the producers of such additives, before using with a copper feature.
Our own pond is a wildlife pond and has a copper feature in the centre, as you might expect. We never use chemicals in the water and the frogs and pond life have been perfectly happy for many years. Try to keep the water sweet by introducing oxygenating plants into a pond. These don't have to be huge things and can even be floating plants so you don't even have to provide any soil, just throw them in. It's always better to try and work with nature and create a balance, than to stress too much about keeping everything pristine, it is a garden after all.
For further advice on keeping fish in ponds with a copper water feature, you should seek professional guidance from a fish specialist.
Metallic Garden accepts no responsibility if these guidelines are not followed.