Tropical Paradise

Artificial decorative ponds

Monday 9 December 2019

Hello neighbours

Seeing your pond and briefly talking about it with you last Saturday afternoon inspired me to think more about such things and start drafting some general advisory notes in relation to them.

So, here are some more thoughts for you, including some specifically related to your situation.


for any cracks in the concrete, I mentioned Sika brand sealants, non silicone, particularly Sikaflex, very good stuff, remains flexible for many years

for use on concrete it may need epoxy resin applied first, to give it something smooth to stick to

but good 2 part epoxy is easy to use and not expensive

high quality non silicone sealants are good not only for external things but internal too – kitchen, bathroom, laundry

silicone sealants are easy to apply but soon become ineffective and longer term are trouble


in such a small restricted area a pump above ground would be obvious, or at least its cover box would, partly spoil appearance of general area

also noisy, annoy you and neighbours, spoil quiet ambience of pond area, could cause hum inside house, may result in you being reluctant to run it

also some chance of pump being stolen, if no fence separating it from public land

depending on ground levels pump could be put a long way from pond, other side of property if you choose

but needs relatively large pipes over that distance, could be difficult if paving eg concrete or bricks in ground between pond and pump location

and would still be noticeable and make noise, would just do those things somewhere else rather than near pond, maybe annoy neighbour on other side

better to put pump close to pond under ground in small pit, cover with soil, let lawn grow over it

pump and pipes then invisible, no audible noise, no chance of pump being noticed or stolen

use submersible pump, no problem having no cooling air flow because pond water flowing through its chamber cools it directly, perhaps also slight cooling from surrounding soil although I assume insignificant

see what good quality submersible pumps of appropriate pressure and flow capability are available new, look at reviews (with caution, as with all reviews)

then look on eBay, Gumtree, likely get good used one relatively cheaply

just don’t buy cheap chinese crap (but you knew that)

ensure that you use a good filter with it, sufficiently fine to keep out anything that could damage pump or clog any sprays it feeds, and with sufficient area so it will not become blocked too soon

more on filtering below

ensure that your pump will not be damaged if run dry

or protect it from that possibility by incorporating water level switch in pump chamber

water level in pond above ground will be higher than top of pump chamber under ground, so that chamber must be sealed perfectly, or nearly perfectly

strong cylindrical plastic container with screw lid with O ring seal would be fine

eg chemical supply container, should be easy to get, maybe free

ensure no dirt or anything else in seal, immediately before screwing closed take O ring out, rinse it and threads with water, maybe put on small quantity of waterproof grease, assemble

don’t screw it down too tightly, or if you ever need to unscrew it you will rotate container and break sealant around pipes

when ground is wet always ensure container remains full of water, or at least nearly, or it will float up like a boat

same as happens when people drain inground swimming pools in wet ground – even concrete pools float in water – disaster

(seriously – when I was an engineering student the civil engineering students had an annual concrete canoe race)

Water level maintenance

pond will lose water via evaporation

being near unshaded western wall of house it will be warm during summer afternoons in fine weather, meaning more evaporation loss than if it were in cool shaded position eg under trees among ferns

manual topping up is not hard, do when you water garden if you do that manually

but that’s no good if you’re away for even just a few days in hot weather, all dries

if you are not present to see your pond all dry you may not care, but for pond visible from street you may prefer it to continue looking as it should

and if it’s obviously recently abandoned it could tell the world that your house is temporarily unoccupied, invite burglary attempt

you could install simple float valve to automatically keep water level up

connect it directly into water supply, with its own isolator valve

or through tap somewhere else, which would be cheaper but maybe messy

as for pump, you can put float valve chamber in ground close to pond, but top of chamber would need to be above ground to permit space for float

also as for pump, depending on ground levels no need for auto level float valve to be near pond, could be other side of property

but in this case that’s much simpler because only single relatively thin pipe is needed to connect to pond, eg cheap 12mm irrigation pipe, not two larger pipes as for pump

more convenient if close to pond, with isolator valve hidden behind rocks, then when cleaning pond can shut off water supply right there, but could be tampered with by someone walking in off street unless it’s hidden behind a small shrub, which could be impractical there

if farther away, behind fence, where no one can walk off street and tamper with it, should not be too inconvenient – you need to get and return your rake, hose etc anyway


if reinforced concrete slab remains wet then steel reinforcement in it will eventually rust and weaken, may result in slab cracking

or destroy slab from inside by expanding and splitting concrete as rust forms on metal, term “concrete cancer”

house foundation slab should be well protected from ground water by strong plastic barrier sheet, so any leakage from pond should not damage slab

unless for some reason leakage results in water going over edge of plastic barrier sheet and being caught in it, worse than being able to run away through ground, although unlikely

if pond structure is built on house slab then any leakage could cause flooding in house, as you mentioned

I wonder whether house builder sloped that part of slab slightly away from house for that reason

leakage into ground could be slow and impossible to notice yet still be doing damage somewhere

whether it is easily noticeable depends on relative rates of evaporation and leakage loss

while evaporation loss is much greater than any leakage loss, as in hot dry summer weather, you may not notice extra loss from leakage

in pond with relatively broad surface area exposed to air but only small depth any leakage loss would be very difficult or impossible to detect by observation of water level

automatic water level maintenance is convenient, never need to top up water, but hides any loss from leakage, so you may need to monitor that

moisture sensor in ground under pond would not be difficult, poke steel rod in to make deep enough hole then slide sensor and cable into it and let ground close again

more difficult with slab under pond though

ground moisture sensor would tell you if leakage happens in summer and early autumn, when ground would be expected to be dry

no big deal if it happens in winter because ground is wet anyway and rain will usually keep your pond full, likely overflow it

but certainly problem in unlikely event of water overflowing into your floor slab plastic liner


install broad screen filter under water near one end of pond, near pump

ensure top edge of filter box is low enough so always under water in normal system operation, never exposed to air, or only very briefly, even in strong swirling wind

wedge shape filter box could be installed approximately flush in sloped end of pond floor, if cutting concrete for it and pipe connection is not too difficult and would not result in any structural damage or failure

or install outside pond, slightly above ground level, behind rocks so not noticeable from street

if above lowest water level it will need its own sealed box

in that case ideally clear window so you can see inside it

perhaps also small skimmer box as for swimming pools, works well if water level is kept near enough right, but shallow pond depth may not practically permit it

may be excessive and unnecessary for this application anyway

still need fine filter before pump – perhaps incorporate as second filter screen in same box as main filter screen, under it

no sand filter as for swimming pool though – a big lump you don’t need


after cleaning, installing pipes, filter box etc and sealing everything, you could paint concrete surface appropriate colour, eg light blue, like swimming pool

paint must be good quality waterproof, not damaged by any chemicals you would ever use to clean pond surface, long life, remain flexible in strong sunlight for many years

good swimming pool or marine grade paint

make sure any sealant you use is paintable with any such good paint appropriate for purpose

paint wlll then form slightly flexible membrane, effectively water container, supported by concrete under it

while paint remains intact, if water level is never above top edge of paint no water can contact concrete, and none can leak out through it, even if unsealed slight crack is present under paint

painting will eventually need to be redone, not a difficult job


after checking, cleaning, installing things, sealing and painting, you could easily install soft subtle lighting

put under or among rocks, so light emerges from under them and lamps are not directly visible, never shine directly into anyone’s eyes

maybe also at tops of spray nozzles, to shine up into water sprays

put lamps and their cables against house sides of vertical pipes, position least noticeable from street

small sealed waterproof LED lights should be easy to find

maybe not from swimming pool accessory suppliers because their underwater lamps may be larger, but they may sell small ones or know who does

ensure your lamps and their wiring are installed such that no rake, broom or brush used in cleaning pond will catch on them and damage them

maybe seal them into place with same sealant as for concrete cracks

run lamps at less than rated voltage and current, so they never burn out, no concern about need to replace them

Dealing with undesirable growths

quick wash with cheap chlorine bleach or diluted hydrogen peroxide is good way to kill and remove slime, algae etc

better prevent than cure though

small quantity of Starver could do job well

it works by starving slime, algae of phosphate by forming insoluble phosphate complexes which precipitate out of water

a brilliant product – it’s why public swimming pools don’t burn your eyes with chlorine as they did when you were little – much less chlorine needed since Starver became available

it’s available in granular and liquid form from swimming pool accessory shops

if use granular, it needs to be under water but not easily disturbed

small mesh container or bag in filter box would do fine

General cleaning

obvious need for some manual cleaning to remove mess, small twigs, leaves, seeds, dead insects etc

sometimes lift out, sometimes rake or sweep out

occasionally sweep most of water out then give it all a quick blast with garden hose, good practical way to clean external hard surfaces (even if the greenies wouldn’t like it)

obviously, never use scourer to clean surface, only soft broom, brush or cloth

If it’s all too much trouble

other option is to remove pond entirely

could all be done for you, if you advertise moss rocks for free provided that the taker removes all the other bits too

could all be taken away by a builder who has desire or buyer for rocks and easy way to dispose of other bits

maybe put lawn instead, or garden bed with small plants

or plant trees or shrubs which will grow tall and shade west facing wall in hot summer afternoons

or maybe mixture of those things

if pond is built into house slab then trees or shrubs of any good practical size will not grow there, at least not without eventually falling over and maybe injuring someone in the process

planting trees in street verge lawn is always an option, but it’s narrow

and you have your tall palm trees anyway

I will be interested to see how it goes

perhaps you will soon have your own happy little tropical paradise, right there

maybe complete with hammocks strung between the palm trees and drinks with funny little umbrellas sticking out of them

While I think of it – quick advice for watering lawns

obvious way is a sprinkler or soft spray

but before any significant quantity of water has gone deep enough into the soil to be really good for the grass water starts to runs off and be lost

better water by very slow dripping

for lawn which is not flat, eg street verge lawn which has a long peak, lay hose along peak, or even slightly to the uphill side of that, not half way between footpath and kerb

leave for 2 or 3 days, let water spread and soak in deep

then resist temptation to do any more watering for at least many days, even in hot weather – watch how the grass responds

roots will follow water down into ground, grow deep to get it

result is much stronger more resilient healthy lawn which is practically immune to extremely hot dry weather, still producing fresh green shoots even when ground surface is dry

not weak lawn which has only ever bothered to grow roots close to surface so dies when that dries

even in hottest weather no need to water for maybe 2 weeks, lawn still healthy deep green, new shoots still growing

does not work with excessively sandy soil though, water falls through it rather than soaking across and down and being held in it

if soil is sandy you may need to dig sand out to good depth and put in some more absorbent soil, or you will never have really healthy looking lawn

Adelaide clay soil is much disliked and criticised by people but can be good for lawns

worst way to water lawn is blast from hose, wets surface only, no depth, gradually washes away soil, any surviving grass soon becomes weak yellow patchy with large hollow bare spots between where soil has gone

tortoise 1, hare nil

That’s it for now

That’s my quick initial thoughts for you.

I assume much good information and advice about decorative artificial ponds is available on the internet.

But, as in anything, you may find some bad advice too, so you may need to be careful.

I have not looked for any yet though. I’m sure it would be interesting, and no doubt I have missed thinking of some relevant points, but for now I’m resisting the temptation.

People who supply good sealants and paints for swimming pools and ponds may have good related advice to offer too.

I’ll leave this page up for a few weeks to give you time to read and copy the content above, if you would like to do that.

It’s not publicly linked, and it’s blocked from being searchable from within this website, so no one else will find it.

I ask that you keep this confidential, and not forward the page address or my contact details without my permission.

Any comments you have about any of this or your experiences with your pond would be welcome.

Best regards

Laurie Williams

Howard Street (temporarily)

0411 501 198