Snails, Mussels and Other Livestock for the Garden Pond
Snails are useful for devouring filamentous algae and rotting vegetation. But it is important to get the right species as some will do considerable damage to plant life if given the opportunity.
The only species that can be unreservedly recommended is the ramshorn snail, a pleasant fellow with a flattened shell like a catherine wheel which the creature carries in an upright position on its back. The shell is deep brown, or sometimes black, while the snail within may be red, white or more usually black.
Some nurseries mistakenly sell the freshwater whelk as a pond snail, and while it is true that it will feed upon algae, it much prefers to chew the broad verdant pads of waterlilies. This is an easily recognised species with a tall, pointed and spiralled shell which houses a greyish snail.
A number of other species are not infrequently offered for sale, amongst them the diminutive ear pond snail and the wandering pond snail. Both look superficially like the freshwater whelk, but are considerably smaller, the ear pond snail being further distinguished by an extra large aperture. Neither is generally destructive to plant life, but owing to their small size must be introduced in greater numbers if they are to be effective.
There are no hard and fast rules as to the number of snails necessary for a particular volume of water, although there is little sense in introducing fewer than a dozen to the average pool. With algae-eating species the population will quite naturally rise and fall with the availability of food. Thus the greener the pool the more snails it will support. Likewise, the more abundant the aquatic plant life, the greater the population of undesirable snails will become.
When undesirable species have been accidentally introduced into a pool they can be captured with some degree of success by floating a fresh lettuce leaf on the surface of the water. Snails will congregate beneath this and can then be removed and discarded. If a fresh leaf is introduced daily, surprising numbers of snails can be captured over the period of a week or two.
It is, of course, preferable not to introduce undesirable species in the first place. But apart from misguidedly buying the wrong kind, they are often accidentally introduced as eggs on the feet of birds bathing in the shallows. Or more frequently still on freshly purchased plants. All new plants should be carefully inspected before placing in the pool and any snail eggs removed. It is not necessary to discard those that appear in a flat pad of jelly as these belong to the desirable ramshorn snail. However, any that appear in a cylinder of clear jelly should be removed, as they are likely to have been produced by the troublesome species.
Mussels can be useful inhabitants of a pool, but a prerequisite for success is a natural floor or a good accumulation of mulm in which they can shuffle. A clean pool with well scrubbed walls and floor will quickly bring about their demise. The putrefying remains of just a couple of mussels will cause considerable pollution.
There are two species of mussel popularly used. The swan mussel, which has an oval brownish-green shell with a white fleshy body and the painters’ mussel, a smaller kind with a yellowish-green shell marked with brown. Both filter water and retain minute suspended aquatic life assisting with the clarification of water and thus making a significant contribution to the well-being of the pool.
Other Livestock for the Garden Pond
Before departing fromand other livestock, I must just make a mention of native creatures which may enter the pool of their own accord. Pool owners often feel concern if they discover frogs, toads, or newts in their pool. I have even heard of some pool owners removing the poor creatures and destroying them in case they were preying upon fish.
Generally speaking, all native amphibians are welcome additions to the pool community, feeding exclusively upon insect life and not interfering at all with the fish, snails or plants, nor affecting the balance of the pool in any way. Indeed, the garden pool is the last retreat for many of our amphibians, for their natural habitats have been rapidly depleted by landand modern farming techniques.
Of course, most amphibians only spend their breeding life in the water, the rest of the time scampering about the poolside and eventually hibernating in some secluded corner. Their tadpoles are an excellent live fish food and a constant source of amusement. The only problem that may occur with a frog in the pond is the attachment of a solitary male to a fish. This only occurs when there is no female present, the frog clasping the fish around the gills in typical breeding stance and causing considerable damage.
Other creatures which are sometimes introduced to the water garden are the turtles or pond terrapins. There are five different species of these lumbering reptiles which are hardy in Great Britain, but only the European pond turtle and Spanish terrapin are at all common.
These require a considerable amount of space if they are not to create havoc amongst the waterside plants. They are also carnivorous, and while usually directing their attentions towards leeches, worms and beetles they are not averse to taking a small fish or two.