The keen gardener who is interested in a pool purely as a medium for plant cultivation, a novel environment in which he will grow to perfection some of the most beautiful of all, will, no doubt, be itching to move on to the chapters describing pool stocking and the plants he can use to ornament the pool and its surrounds. That growing aquatic plants was the only reason for making a pool – that it is a great pity if the other decorative possibilities of water are ignored.
I believe that if the surface of the pool remains completely placid, and the only sound is the occa sional plop of a rising fish, then one of the greatest potential virtues of the water garden is being neglected. Arrange for the water to move, and immediately the spectrum of water gardening pleasures is widened; the pool delights the ear as well as the eye. The splash of a fountain and the murmur of a waterfall make restful, refreshing music and create atmosphere as no other garden feature can. Quite apart from these aesthetic considerations, there are practical benefits from moving water. There are also sound practical reasons for ensuring that the amount of movement is not excessive.
Fish revel in the splash of fountain and waterfall. Every bubble carried below the surface by the cascade, and every droplet from the fountain spray, increases the oxygen content of the water. In close, thundery weather the unhappy gulping of fish at the surface, due to a temporary crisis of oxygen defi-ciency that sometimes has fatal consequences, is completely avoided. Moving water, then, is a good thing, but we must be careful not to overdo it.
Water plants are not so happy about moving water andin particular dislike cold water and strong currents. So it is not a good thing to have a stream, either natural or artificial, flowing through the pool. Neither is it a good idea to have cold mains water running continuously into the pool; the fish might not object, but certainly would and the local water board might not be too keen about it either. Such an arrangement is quite unnecessary.
The cardinal rule of any moving water arrangement is to circulate water from the pool itself. To do this all you require is an electrically powered pump to push the water through the fountain jet, or lift it to the top of the watercourse. Gravity brings it back: the water goes around and around, slightly cooled but not made cold, and currents are kept to a minimum. You do not need an external water supply, or elaborate plumbing, or an overflow arrangement. The fish are happy, the lilies are happy, and so, presumably, is the water board.
At this point I ought, perhaps, to mention the one thing that a fountain or waterfall can not be expected to do. Contrary to popular belief it will not make green water clear. There are a number of practical steps that can be taken to prevent or cure the ‘pea-soup’ condition, but circulating the water is not one of them. Indeed, if we are unwise enough to create a powerful torrent, the violent disturbance of the water might well distribute mineral-rich mulm from the bottom into the upper water layers and encourage the continuous production of green-water algae. This is another reason for keeping water movement to a modest level. There is no disadvantage in this. A murmuring splash is the pleasing sound we want to hear, as from a babbling brook, not a miniature Niagara.
Whether you have a fountain or a waterfall (or both) is a matter of personal taste. I think it depends largely on what is appropriate to the shape and setting of the pool. A stream and waterfall is a natural phenomenon; it looks fine in a rock garden beside an informal pool, but is difficult to associate convincingly with a formal rectangular pool. The geometric shapes of rectangular and circular pools are the logical setting for the formal symmetry of fountains, which have no counterpart in nature.
With the availability of submersible pumps that simply sit in the water, and require no connection except to the power supply, a fountain is something that can be added to a pool layout at any time. If a waterfall is contemplated it is as well to plan for it at an early stage and carry out what little construc-tional work is involved before stocking the pool, to avoid subsequent disturbance, which is the reason for dealing with the subject at this stage.