Your pond questions answered

Got a question about your garden pond? Chances are you’ll find the answer there!

My newly installed pebble pool looses water

This is because you did not correctly adjust the height of the fountain jet

All fountains should obey a fountain rule, that fountain rule is called the “jw rule”. The J.W rule states that the height of water emanating from a fountain / water feature should be no more than 50% of the diameter of the pool in which it sits.

This is because water will fall / blown as far as it is high.

So for example if you have a pool that is 4 M* across if you have a jet that is 4M* high in this pool that means water can fall 2 m outside of the pool. Obviously over time this will empty the pool. this applies to ANY pool.

There are certain “Exceptions” such as if you have a large surface, such as a rock or wall where the water runs down its surface, or wind controls to reduce jet height in high winds, auto fill to compensate for water loss.

When designing a fountain or adding a fountain to your pond / pool this rule must be taken into consideration

* your choice, be it metric or imperial unit of measurement

I have used a cheap liner for a pond is there anything i can use to stop it from cracking?

Cheap pond liners split / crack after time because they are affected by the sun’s ultra violet rays (it literally breaks down the material) you can over come this by raising the water level in the pond, if this is not possible, you can cover the exposed parts with something that is harmless and will not affect the water. But you will probably spend more doing this than if you used a good quality liner in the first place.

I have 3 pumps but only one supply cable how can i safely connect them?

You need to use a “switch box”.

If you have a waterfall that leaks, what can you do to repair it?

Unfortunately you should remove the whole waterfall (sorry) and place a liner behind it with the bottom end of the liner going into the pool, this is so that if you waterfall leaks any water will not be lost and be returned to the pool.

If your waterfall is still being constructed then you can use a sealer such as G4 to seal all waterfall surfaces, but if it has started to leak, it is doubtful if G4 will work due to any large cracks you may have (even if you can not see them) the best option will be to take your waterfall apart and rebuild it with a liner behind AND use G4

I want to use a washing machine pump for a waterfall, is this OK?

In theory yes, they pump a lot of water, in practice no, because they are only designed to run for a few hours a day everyday, also they are not designed for outdoor use.

I want to build a small water feature but I want to use a solar pump, any suggestions?

Yes, use mains operated pump. This is because most solar pumps are designed to float on a pond (which is not good) they also need very bright sunlight to operate ( I recall seeing a tv shopping channel selling them and they would not work under the very bright studio lights)

You must also remember that solar pumps only work in bright sunlight, so most will not work on an overcast day or at night when they do work they only have a small pump which can not provide a lot of water.

I have a new pond that is at the other end of the garden, I want to have a pump and filter – I want to have solar can you suggest one?

Simple answer no.

This is because filters need to be on 24/7 if its solar it will only work on a bright day, also a filter works best if there is a uv light fitted too, but there is no such thing as a solar operated uv light

Solar pumps are also good, but not fantastic, the good ones also cost a lot of money, see question above

Is it true that running water never turns green?

This is not true at all. streams, brooks and the like never turn green because it is not the same water running, in a water feature, pond or similar it is the same water running around and around so yes it will eventually turn green, if only some water is exposed at any one time, say through a rock then back to a covered sump, the amount of time the water is out for is short so it will take a long time before it turns green

What size pond filter should I have ?

Basically a pond filter size should be such that it is at least one third the size of the Surface area of your pond (some koi people say at least one half) so for example if your pond is 10 x 9 (total 90 square units) then one third is 30 units.

However this does not mean that you filter should be say 10 x 3 units) to equal 30 units) it is the surface are of the filter media.

What size hose should I use for my water feature pond?

It actually depends on how much water and how far you will be moving it, so for example if you have a water course that is say 6 feet long and say 8 inches wide then a 1/2 inch hose will work, but you will get a poor water flow, this is because of the resistance of the actual hose, you will be better off with a 3/4 inch hose.

Also any bends in the hose will also add to the “resistance” the worst is the 90 degree bend, you will be better off making a sweeping turn rather than a sharp 90 degree bend

Also it depends on the pump flow rate, you should always use the biggest hose that your pump will connect to (if using a hose tail, remember to cut it to the size of your hose) some waterfalls you may see in theme parks and the like have 4 or 6 inch pipes, sometimes bigger feeding them.

The brand of hose is your choice, but “spiral” hoses are better, since they can not normally be squashed

Noisy Biological filter

Noisy pond filter, me?

If you have a pond with a biological filter (as most of you will) does it return water via a pipe at the top of the filter (or the bottom) falling strait back into the pond?

It probably does, but let me ask you this. Is it noisy? no of course it isn’t or is it? Suppose your pond is in a courtyard or similar do you realise that the sound of the outlet water hitting the surface will be amplified especially when the ambient noise (traffic) level falls in the evening, have you considered your neighbours? To you it is nice and an essential part of your pond to them it’s gushing water that is annoying.

What can you do to stop the noise? Put it on a timer? NO! all biological filters should run 24 / 7.

Most biological filters the outlet is a standard pipe size, so the simplest and cheapest thing to do is to add a bend onto the outlet and a new pipe from the bend to just above the water surface as I have shown below

If your filter outlet pipe is not a standard size you have 2 choices. Either remove the pipe and make the hole to a standard pipe size (best idea) or put a bigger pipe over the whole outlet and fix with silicone on the inside of the new pipe.

You could also install a “water fall” instead, but one which starts from just under the filter outlet and finishes just above the water surface

But what about pond aeration I hear you ask? that’s the point of having the outlet high up to aerate the pond. I would recommend that you install a fountain in your pond as not only will this aerate the water it will also look very nice, but do put the fountain on a timer NOT a photocell as the daylight will mean it will start in the early hours.


I have a metal tank that I am going to “seal” but can I bring the pump cable through a hole in the side and put mastic on it to seal it?

The simple answer is NO, the metal tank may cut into the cable, also if the cable ever moves you will have a leak, you should use a proper connector to take any cable through a wall, that is why most people go “over the top” with pump / light cables

I have a very big and deep pond (4 feet in the middle) can I use an ordinary pump for a fountain?

Yes you can, but to stop it getting clogged too often I would suggest you stand it off the bottom of the pond floor, a couple of bricks although crude works very well.

U.V and new pond?

Q: New pond, have installed fishmate9000 and tetra pressure filter return by waterfall. I’ve heard this should be left on all day and night with the exception of winter. I don’t mind but is this necessary and would you recommend?

Also, as it’s new, filled from the hose I’m running it just now and imagine the filtration will build up the necessary “stuff”, but should I add a water conditioner or just get some plants in for now?

Pond filters should be left running 24 / 7.

The “stuff” is bacteria, this will take some time to grow and multiply, if you have no fish, then I would just leave it to mature, you can add plants no problem.

Can I use a central heating circulator for a water feature?

Advantages: Cheaper, costs less to run


Needs valves to connect to pipe work, must be protected from elements, not designed for the job

It is a fact that koi pond owners do use these, but they change the actual pump housing to a purpose made plastic version, so that is more cost.

As the pump is steel they will rust over time, which is why koi keepers change it. In its normal use that of central heating, the water is in a continuous loop, so it can be almost anywhere on the system.

But a water feature is NOT a closed system (air gets in at the feature) so in order for this to work you must have the pump lower than the sump, and as the sump is in the ground the circulator will need protection from the elements

So yes you can use one but for a water feature it is going to cost you more than a submersible pump will.

Is a fibreglass pool for a pond a good idea?

Yes, if you can get one. I say if you can get one, because they are big and bulky, but do not weigh that much (for the size they are) and unless you collect it yourself, (a reasonable sized one will not fit on or in your car) courier companies are reluctant to transport them since they charge by weight, and need a big lorry to carry them. They are expensive to buy, but they will last a lifetime. Oh, and get a dark coloured one, since as its a pond if its light in colour it will soon show any algae / general dirt

Fibreglass pools also have a “unique feature” when you see all the different shapes and sizes standing against a wall (that is how they are usually displayed) they are huge, but when you dig the hole and put them in they “shrink to about 2/3 of their size”

They don’t really shrink, it’s just that when they are standing up they really look huge, but when you install them they no longer seem as big as they were, so if you are going to get one, get a really big one. (If you look at a well known auction website, the sellers are “collection only”) Because they are so awkward to transport.

My pond water level is dropping quickly, my box filter looks wet on the outside, what do you think is the problem?

It sounds like the filter media / sponges are clogged and so the water is not getting through the filter quick enough, or you filter outlet is blocked. (I myself once had a piece of filter media that got wedged in the filter outlet) If the filter has sponges you should clean them as and when required in pond water, tap water will kill any good bacteria

More about pond filters

How does it work?

The filter media is home to millions of micro bacteria (they soon reproduce) they live off the “nasty” bits in the water (its actually called the Nitrogen Cycle, but i will not bore you with the chemistry) the “nasty bits” actually come from the fish. Think about it, living in the same water day in and day out. You have a toilet, fish don’t

Getting a filter

You can get a filter from all aquatic shops or via the web, you can also make your own, this is a guide as how they work and what size you should get.

Filter size

See comments on size above.

Filter media

There are too many brands of filter media to list, but they all work the same way. Each type of media has a surface area, all are different shapes / sizes to each other to give “the best surface area” the choice is yours.

Filter media should not be confused with filter sponges (most commonly available “box filters” have 3 layers of different coloured sponge, varying in coarseness, this is to remove particles from the water before it gets to the filter media itself. some filters have brushes or / as well as layers of foam these also serve to remove particles from the water.)

Filter box

Most “off the shelf” filters are just a plastic box with filter sponges and filter media and a “spray bar” the spray bar is usually just a pipe “blocked” at one end with holes drilled in it this is to give an “even spread” of the incoming water. the more expensive ones also have bottom drains to make it easier to clean the filter (operate the valve and it lets out all the water / sludge build up)


Pond filters should be cleaned at least once a year (more often depending on how clogged the filters get) when cleaning a filter you should only clean the sponge layers not the filter media, this is because the media is inhabited by millions of microscopic bacteria that are doing a good job, if you clean the media you will wash them all away, but the sponges do become blocked, and so will need cleaning, but you should use a bucket of pond water as tap water contains chemicals (safe to us but not bacteria) which will kill the helpful bacteria.

Flow rate

Now you have chosen a filter what about getting the water to it, The size of pump depends on volume of water (including that in the filter) it should be capable of pumping the entire volume of water through the filter every 3 – 4 hours so if your pond is say 1000 units then you will need a pump that can pump 250 units / hour minimum

When choosing a pump its maximum head should also be taken into consideration, this is the height to which the pump can pump water up to. In this example you do not want a pump that can pump up to 250 units / hour at 0 feet (this means at a higher level the pump can pump say 150 units up to 3 feet which is not what you want, you want 250 units at the height of your filter.) You should also take into consideration the size of pipe you are using any bends (less bends the better) and also your U.V.

Returning the water

Once the water has been filtered the easiest way to return it to your pond is via the filters outlet pipe, hanging over the edge of the pond. However this may not fit in with the decor of the pond and you may wish to construct a waterfall. Although doing this you should be aware of the noise the water will create (especially at night when there is low ambient noise) some people have the filter return via a waterfall but with a very short fall from the edge of the fall to the water surface, so they still have a waterfall which looks nice but low noise. You may also want to read this

Over wintering

Although in the colder months the bacteria will stop working, i recommend that you raise the filter pump (stand it on a couple of bricks) turn the pump flow rate down, also remove the U.V clarifier (so if the water freezes the U.V. will not be damaged) this is just to keep the filter “ticking over” I am of the opinion that if you turn the filter off when you turn it back on you will be dumping a whole load of dead bacteria into the pond


I mention “units” as this avoids confusion, your units could be gallons, litres, feet or metres, please use the appropriate units for your country.

Originally written for Featured image by Couleur, fish photo by Peter Timmerhues both from Pixabay.

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