Your Top Pond Questions Answered

We love all the comments you pond lovers add to our articles. Many of the comments address the same kinds of issue (but do keep sending them in!) – so we’ve taken four comments which we feel reflect what a lot of people are asking and our expert has answered them below. We hope you find this useful.

Snails Dying

Hi there, I wonder if you can help me? Over the past week or so all the snails in one of my ponds have died. They have all changed colour from black to light brown. Other pond life appears unaffected. Any suggestions what the problem is? 02/06/12
 

That certainly is a strange one. The two things which instantly spring to mind are some kind of poisoning, or maybe an infectious illness that clearly only affects snails. Since you say that the deaths have happened in one of your ponds (and so I’m assuming that if there are any snails in the others, they have been left unaffected), poisoning begins to look the most likely.

If you can safely rule out the possibility that any slug & snail-specific pesticides or biological controls could have been washed or wafted into the pond – and there’s no chance that anyone has been a little too enthusiastic with the slug pellets – then my bet would be on the copper level in your water having risen. Just like the copper rings to control their garden cousins, aquatic snails are particularly sensitive to this metal – so it’s probably worth testing your water to see. It will probably mean a water change, then trying to track down the source and work out why it’s only affecting that one pond, but once you’ve done that, everything should be back to normal.

If the copper angle proves inconclusive, however, snails are prone to their own particular set of diseases and parasites, so keep a careful eye on your other ponds for any signs of ill-health and be prepared to isolate any affected molluscs swiftly, to control the spread.

Frog spawn disappearing

Like others, our frog spawn has completely disappeared for the last 2 years. After last year’s experience, we covered the pond with netting so no predators from out of the pond could get at the frog spawn. We has 15-20 large ‘lumps’ of spawn but again it has completely gone. We have carefully checked the pool and there are no tadpoles. The pond is 10’x4′ and up to 3′ deep. We have no fish but do have some newts but do not think they could have eaten so much so quickly. Before the last 2 years, the pond would have hundreds of tadpoles in from which we would see quite a few froglets. but none for 2 years. 11/04/12
 

Unfortunately, as you are obviously aware, what you are describing is becoming an increasingly common – and very depressing – tale. Covering the pond after spawning should certainly have prevented the usual suspects from getting at it, and likewise, I think it’s safe to say the newts are in the clear, which means something else has to be going on.

Water quality has been implicated in a number of instances of ‘vanishing spawn’, since factors such as the pH balance, nitrate and oxygenation may adversely affect the viability – and in some cases, the integrity – of the spawn itself. Since you say that you don’t have any fish in your pond, you may not do the number of regular water quality checks that fish-keepers tend to have to, so it might be worth buying a simple test kit from your local supplier and seeing if that throws any light on things. It’s also probably worth getting in contact with your local wildlife trust, to see if they know of any problems with frog health in the area. As you probably know, chytrid fungus is having serious impact on amphibian populations, so if your frogs are ill, or the population is otherwise in decline, it could simply be that the viability of their eggs is dropping.

There’s nothing else to do this year, but assuming your frogs return next spring, perhaps you might consider collecting some of the spawn and putting it into a tank indoors. If you keep a close eye on it under controlled conditions, you might just find out what’s really happening.

Fish dying suddenly after years of pond keeping

We have had our garden ponds for over 20 years but today our fish have started to die. Even when they are dead they look healthy, bright eyes good colour etc and. no visible signs of disease. Have you any advice please? 02/06/12
 

How very sad for you; I’m sorry to hear about your problem. After looking after your fish successfully for so many years, I’m sure you’ve already thought of, investigated and ruled out all the obvious things that might possibly have caused it – water quality issue such as nitrate levels and acidity/alkalinity, de-oxygenation as the water has begun to warm up, and so on. If your routine water tests aren’t showing anything out of the ordinary, then it’s probably time to start thinking about some of the more unusual possible causes.

I’m not quite clear whether they have been dying en mass, or more gradually in ones and twos, but given the absence of any signs of damage or disease that you describe – and assuming they haven’t simply succumbed to old age – it’s beginning to sound as if some sudden change has occurred within your pond. If that suspicion is true, then there are two things which immediately come to mind, namely poisoning or electrocution. Have you, or any of your neighbours been spraying pesticides recently, or using any chemicals on your gardens? If so, is there any chance that it might have drifted, or been washed into the water? A lot depends on the volume of your pond, but that might be a possibility to explore, particularly if other forms of aquatic life start to show any ill effects.

It might also be worth having a qualified electrician check over your pump and any other electrical equipment too. No matter how well you maintain them, the years can still take their toll and very occasionally this means that they will cause problems, so it’s definitely a case of better safe than sorry!

Can’t grow water lilies

I have a pond with a variety of fish – but I have never been able to keep water lilies. I have been told that the fish eat them – is this true and is there a variety that the fish don’t like? 27/05/12
 

It depends on the particular mix of species of fish you keep, but the simple answer is yes, I’m afraid that it is true. Many kinds will happily eat water lilies – and most other types of pond plants too – when the fancy takes them. Probably the worst offenders tend to be Koi, which are notorious for grubbing up artistic planting arrangements and then munching away on them, but most members of the carp-family (and that includes goldfish, shubunkins, comets and many other common varieties of popular ornamental fish) will have a go from time to time. Exactly how much damage they do tends to vary quite a lot, from a few mildly damaged leaf edges, to out and out destruction – and from your question it sounds as if your fish definitely fit into the committed lily-eater category!

Unfortunately, there doesn’t seem to be much general agreement amongst pond owners on any one particular type of water lily that’s especially unpalatable to fish, but if you really do want to be able to enjoy these lovely aquatic plants in your own garden, there are a few things you could try. One option, if it’s practical for your pond, would be to fence off a section of deep water with suitably sized plastic mesh, to make a fish-proof underwater fence, and grow your lily behind its protection.

Alternatively, you might like to consider giving up on the idea of their peaceful co-existence altogether, and simply construct another pond just for the plants. It needn’t be a big undertaking; there are dwarf lilies such as the tiny flowered Nymphaea pygmaea “Alba” or the variety “Aurora” which will do very well in a tub or barrel – so the good news is, you don’t have to miss out!