Pond Cleaning & Maintenance – FAQs

Water Gems pond maintenance, weed control spraying


Nick Benge
07734 386243

Common Problems with Ponds and Frequently Asked Questions

We often get asked for advice about ponds and so we have put together some FAQs as well as general advice in our Pond Tips section on our News page.

If you can’t find the answer to your issue please get in touch,as we can provide a makeover service and provide advice to restore it to its former glory.

1. My pond is leaking – what can I do?

2. Why is my pond water green?

3. My pond is overgrown.

4. Invasive alien species in ponds

5. What fish should I have?

6. How do I build a wildlife pond?

7. Formal water features.

My Pond is leaking – what can I do?

Probably the commonest problem that we get approached with is a pond that is leaking and there are various steps you can take to diagnose what’s going on

  1. If you have a pump and a stream or waterfall and the pond is going down, turn the pump off and the fill the pond up. If you do not get any water loss then, it means that the problem is either in the hose from the pump to the top of the water course, or in the water course, which is actually the commonest cause.  If it is in the water course, put the pump back on and see if you can see anywhere where the water is actually leaking out the sides either over a liner or through concrete or whatever.  Once you locate it, you can fix it.

2.  The other thing that can happen is simply debris accumulating in narrow points in the stream or cascade backing the water up behind it and it then flowing out the sides, and you lose water that way.

3.  Assuming you have not got a water course, or that the leak is not there, then the other obvious problem is a hole in the liner. Again, if you do not fill the pond up and let the pond drop, it will eventually drop to where the hole is, you can then find it and potentially patch it.

4.  One other cause of ponds going down is a liner that is behind stones or something, somebody stands on the stone, pushes the liner down and the water runs out  over the top of a new low point and you end up with what looks like a leak. If you can locate that, just pull the liner back up and you will not have a leak any more. Back to FAQs

Why is my pond water green?

The most common cause of green water is lots of light, lots of nutrients and maybe a big silt layer on the bottom of the pond.  The phytoplankton – the algae suspended in the water – use the light and the nutrients that are free in the system and cause the pond water to become green.

The simplest solution is an ultra-violet clarifier.  You need a pump, a hose, and a power supply.  You pump the water through the UV and back into the pond. The UV is basically a bulb.  The ultra-violet light breaks down the cell walls of the floating green algae that make the water green.  UV’s are very efficient and very effective.  However, the problem with them is that they do not actually solve the problem, they just mask it.

By adding the UV, and killing the phytoplankton, you very often swap green water for filamentous algae which use up the spare nutrients and light which are still there.  So you can actually end up with almost a worse problem because the underlying cause is excess nutrients. Green water, and quite often duck weed, are often a signal that it is time to clean your pond out. Back to FAQs.

My pond is overgrown.

If you have a small pool and the plants have not been managed for a number of years, you can simply cut them back or pull some of them out.  You do have to be careful however as very often these pools have good water quality because the plants are absorbing the nutrients.  The key thing then, is not to rip out too many of the plants because you can go from clear, relatively nice-looking water to something full of algae, simply because you have pulled too many of the plants out.

If you have a much bigger pond, a lake or a lochan then commonly some of the problems are with some of the very vigorous plants like bulrush or Norfolk reed and these need spraying off, and that is the best way to control them.  Ideally you do not plant Typha (bulrush) or Norfolk reed in ornamental systems simply because they tend to take over completely.  There is also a small-leafed lily called Nymphoides peltata which you have to avoid like the plague and these all need spraying in order to control them. Back to FAQs

Invasive alien species in ponds

The worst of these is Crassula helmsii, the New Zealand pygmy weed.  It is also called Tillaea recurva.  It is light green, will grow in damp ground and under water to quite deep levels and will just fill a pond completely.  It is still a plant, so it still provides habitat for invertebrates and so on but it does out-compete native plants and does not support as much wildlife as native plants.  It is very troublesome.  Once you have it, it is extremely difficult to get rid of other than stripping the whole pond completely back to the liner and starting again.  Back to FAQs

What fish should I have?

Key things with fish are to avoid stocking too many.  If you really pile fish into a small pool it  simply becomes overloaded with nutrients and it will go green and unpleasant.

Koi can be an issue.  They grow very big and eat a lot of food and they are not very keen on Scotland’s cold climate.  They sometimes do quite well but they are probably better of further south.

Golden orfe are a fish I like.  They seem to like cold water, they are visible, they shoal, they breed and they live for a very long time.

Goldfish and shubunkins are also fine.

There is no point in having fish like tench.  You simply will not ever see them and they just do not perform any more useful function in a pond than goldfish would.

Fish tend not to mix very well with other wildlife, simply because they will eat a lot of it but you do get frogs using fish ponds quite successfully and a small number of goldfish or orfe are a nice addition to a small garden pond. Back to FAQs

How do I build a Wildlife Pond

We are often asked to build wildlife ponds.  It is a relatively straight-forward job and you do not need a huge amount of depth.  The key thing is to plant them heavily with native plants – such as bog bean, hornwort, water mint, marsh marigold, purple loosestrife, flag iris – all provide flower for bees and generally habitat for invertebrates.

Sometimes wildlife competes.  It is a very natural situation but adult newts, for example, will eat frogspawn.  However if you just create shallow areas with native plants and leave it alone, then, as they say – build it and they will come!

No need to take silt or water from any other water course nearby; that is often a mistake because often canals or the local pond actually have alien things like Elodea in them and you simply introduce them into your pond.  Much better to buy native plants or get them from somewhere that you know is clean and then all the other invertebrates will colonise anyway.  Frogs, newts and sometimes toads will find their own way to your pond.  I personally do not see much wrong with taking some frogspawn from where there is a lot of frogspawn, perhaps from your local park, and putting it in your own little wildlife pond.  Supposedly you can transfer diseases and so on, but given that the adults spread out all over the place anyway, I cannot see much of a problem and you will get an instant population of frogs. Back to FAQs

Formal water features

Small, formal, falls of water, for example water falling from height from something like a stainless steel letter box are much more difficult to do than they look.  The fact that you have a small reservoir of water at the bottom means that any water loss – a splash, a slight mistake in any of the work – and the bottom reservoir just drains rapidly and you have to keep filling it up.

Because you cannot generally plant them, keeping the water clear can be difficult. You either have to put UV’s and, perhaps, dosing units on them to keep them clean or you have to find some way of introducing plants.  These features look fairly simple, but unfortunately they are not. Back to FAQs


We are leading specialists in the design, creation and maintenance of water features in Scotland. We were founded in 1993 by Nick and Annie Benge and have a strong academic background. We are passionate about what we do.