Help With Everyday Pond Problems
When fish are prone to disease, sudden death and red fins, this is a good sign that the water has a high level of acidity (or low pH). Other indications are when oxygenating plants do not multiply well, biological pond filters do not work properly, or water snails develop thin pitted shells. Remedy:
see 'Alkaline water
When fish are prone to fungal diseases and gill disorders, this is a sure sign that the water has a high level of alkalinity (or high pH). Other indications are when oxygenating plants are covered in a slimy coating, water plants display a yellowing of the leaves when in full growth, and the water smells slightly of ammonia.
Remedy: Whether the water is biased towards acidity or alkalinity, the remedial process is the same. To correct the ph level so that it is as near to the desired level of pH 7-7.5, start by changing about 25% of the water in the pond. Then increase the aeration level, such as by running a fountain or waterfall.
Caused by a vast number of microscopic algae, this is not harmful to fish or plants, but is unsightly and detracts from the beauty of the garden. In new ponds, this effect should clear by itself. If not, install a filter with a UV clarifier, and then when the water has cleared by half or more, add more oxygenating plants to get nearer to the desirable 'balance' of plants to fish.
For a more detailed look at the causes of green water and the remdies availabe, see our dedicated page.
A balanced pond with fish, plants, and perhaps a fountain or cascade will have enough 'going on' to prevent the build up of gasses. If your pond has just a faint odour, then reduce the water level by about half, and use a pond vac to suck up the silt and detritus from the bottom of the pond. Then, top up with clean water. If the problem is acute it is probably caused by a lack of oxygen in the sediment, promoting the growth of certain bacteria, which produce unpleasant gasses, such as methane and hydrogen sulphide - which smells of bad eggs. Drain the pond (after first netting out any fish), extract the silt, and refill it with clean water. Installing a filter with UV clarifier should help to prevent this from happening again.
Leaking concrete pond
To trace the leak, turn off all pumps and filters, and allow the water to drop to the level from where it is escaping. The leak may be in the rendering- caused by excessive exposure to sunlight or general wear and tear. Alternatively it may be in the base concrete, due to outside influences such as plant roots growing through it. A small leak can be repaired with an application of rendering. Where the leak is more serious it may be necessary to install a butyl liner as a membrane, which will maintain the water in the pond. Remember, if roots have caused the problem these will need treating before the liner is put in place. If not, they will continue to grow, and will damage the liner, causing the leak to start all over again.
Pond icing over
The ice layer prevents oxygen from getting into the water as well as harmful gasses being allowed to escape. If snow then falls, it will settle on the ice and prevent light from penetrating into the water for the fish. Melt a hole with a saucepan full of boiling water. Or prevent ice from forming in the first place by using an electric pool heater. Alternatively, run a fountain or waterfall permanently - the moving water never becomes still enough for ice to form.
Common Water Garden Pests
Blackly / Greenfly
In a water garden situation, these should be referred to as water lily aphids. If plants are infested, spray the leaves forcefully with a jet of water to wash the flies into the pond where, with luck, any fish will eat them. However, because these aphids are flying insects, it is likely that your plants will receive further infestations during the growing season.
Water Lily Beetle
The small brown beetles are the most damaging pest of the water lilies. The adult beetle lays its eggs on the leaves in early summer, and then the blackish larvae emerge.
These grubs eat the leaves, making holes on the edges as well as in the centres. Eventually the leaf becomes so damaged it withers and rots in the water. Cut away badly affected leaves and hose the grubs into the water.
The larva, or 'stick grub', of this insect chews into the roots of aquatic plants to make a shelter.
Some plants may suffer a little damage, but it only becomes serious if a large number of the grubs are present.
There is no recommended treatment for the control of these flies. In any case, if there are fish present, the grubs soon become a useful source of food.
The larva of this insect is a green/bluish maggot, which feeds on the leaves of Irises.
During the summer, it will eat holes in the edges of the leaves; a second generation may do the same during autumn. Remove seriously damaged leaves, and pick off and destroy any grubs seen. Where bog garden Irises are affected an application of derris dust will help to control the pest.
These small, green, hopping insects move from plant to plant, and they do most damage to soft, fleshy-leaved marginals at the edges of the pond. Affected leaves will have small pale yellow-green spots on the upper leaf surfaces; in bad cases, the whole leaf will turn brown. Hose the grubs into the water, where fish or frogs will consume them.