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Ask Gerry : Hard Landscape : Garden Pools


, carrickmacross Posted On: March 21, 2015

I don’t know if you can help have found a large amount of frogspawn on the side of the road and it is out in the open with no water any advice would help.

Sometimes frogs mistakenly laid spawn in shallow puddles that dry up. All you can do is transfer it to a garden pond or a natural pool. It may already have dried up too much to survive.

Green Pond Water

, Nenagh Posted On: April 24, 2011

I have a large half water barrel that contain a waterlily, marginals and fish. The water is very green with algae. Is this harmful to the fish? What can I do to maintain the water clarity?

If fish are fed in a pond or barrel, they pass out nutrients which encourage algae.These do not bother the fish.

If you want clear water, you will have to install a biofilter and a UV filter, or no fish.

pond plants

, tralee Posted On: March 1, 2011

what are the best plants for a pond and will any of these survive a winter like we just had.

Bullrush, waterlily, water spearmint, marsh marigold, water hawthorn and flowering rush are good choices, and these are hardy. 

dead frogs in pond

, Celbridge Posted On: February 8, 2011

Our pond was covered in a net from early November until just over 2 weeks ago. For much, perhaps most, of of that time the pond was frozen. Yesterday my son drew my attention to the fact that on the bottom of the pond are many dead frogs. They are bloated but otherwise not decomposed. I’m seeking help as to what might caused the problem and how I might deal with it.


Most likely, they were killed by the hard freeze.

Soil after digging out pond

, Blessington Posted On: July 29, 2010

After making a large pond, I have a lot of soil left (some poor, some topsoil) and would like to use it in our 3/4 acre garden. The back garden is a long rectangle with pond (near house), veg. plots, flower beds but plenty of available space. Any ideas on incorporating this into the landscape of the garden, which is very level and has a great view to the mountains?


The spoil from excavating a pond can either be taken off site and dumped or it can be used in the garden to fill hollows or to make raised areas.

Raised borders can rise from front to back and can be a way of displaying plants better as well as giving them a greater depth of soil. Or you might have some area that would benefit from having a mound of earth.

Ideally the top soil should have been separated from the subsoil and the top soil put back on top of the re-located subsoil. 


Problems with pond.

, Dublin Posted On: April 21, 2010

Pond, 3mx3mx.45M deep, southwest facing, sunny, has ‘Laguna’ filter and UV treatment fitted nevertheless pond always like pea soup. Water plants doing badly, nothing really growing. Pond fed by rainwater off house roof. Frogs seem happy though. Any suggestions on what is wrong?


A sunny pond will have more algae. Rainwater from the roof helps to clear out nutrients from the water, which is why the algae grow,

It might be possible that the filter is too small for the pond and/or the UV lamp is not working properly, as both of these can help a lot.

If you have a lot of fish, and do a lot of feeding, it increases nutrients and algal bloom.

Increase the cover of the water with plants, as this reduces light to algae and the plants use up nutrients.

The removal of excessive plant material in late summer, removes nutrients each time. The pond bottom should have some mud and gravel as this absorbs nutrients.

Looking after a small garden pond

, Lucan Posted On: March 13, 2010

Recently have moved into house with a small garden pond, about 1.5m diameter. As I have absolutely no experience in Pond maintenance, could you help me out please? there already seems to be some algae or other matter formin on the surface. There is some greeenery growing in the pond also.


A small pond is always a biit tricky, Try to keep leaves and other debris out of it. Pond plants help to reduce algae by using the nutrients in the water and by shading some of the surface.

There is a strong likelihod that you will get algae for part of the year, in the warmer months, and it will clear.

Emptying it and clearing it out is not a solution. It is better to allow it to settle and to simply remove leaves and dead foliage of water plants.

pond lining

Posted On: February 17, 2010

I’m planning a pond, about 10 x 3 mtr, wha is a bit wide for standard lining sheets. So, I’m thinking of using clay. Where to get the right type of clay, and helpful instructions on how to do that?


The pond is not too wide as sheets of synthetic rubber can easily be joined with rubber solution, just like an inner tube puncture repair. Lakes and reservoirs of large size are made like this.

Clay for pond lining is a lot of work and not all that reliable. It needs to be heavy pottery clay, or marl, laid 15cm deep, and heavily and evenly compacted.

Why are there lots of dead frogs in my pond

, Kilternan Posted On: February 15, 2010

The ice was at least 4″ thick on my pond (approx size 2m across x 1.5m deep) during the freeze in January. Unfortunately when it thawed out there are lots of dead frogs in it. I never had this happen before and we would get quite a lot of ice most years. I thought frogs usually wintered out of the pond. Do you have any idea why this happened?


Frogs arrive in garden ponds soon after the turn of the year in preparation for spawning and they go to the bottom of the pond where they are safe from frost and predators. There is a good chance they simply froze or the oxygen levels in the water dropped too low under the ice.

water barrel ‘feature’ ideas

, greystones Posted On: February 9, 2010

I have concrete, so a water barrel surrounded with stones and terracotta pots, plus two large bits of tree trunks i want to biodegrade to encourage nature.I would like a small water lily (pink/white) but what nice grass can i also include in the barrel and maybe a third different shaped plant? also in the surrounding pots i hope to plant plants that will ‘wander and creep’ over all things, including the trunks. I have bought some sedums and also ‘golden oats’ I love textures so that is what i want to create around this feature.7


You could try a dwarf bulrush or a flowering rush, Butomus, and the creeping jenny or mimulus to spread.


, tuam Posted On: January 22, 2010

I live in an estate with a down ward slope into my back neighbours gardens are paved so any rainwater flows into mine from theirs,leaving mine left waterlogged!Its like marsh ground in the moors,its even full of rushes!I was wondering could you possibly advise me on the most effective way of draining the water or even incorperating it into a pond/water feature of some sort.I have a limited budget but an enthusiastic workforce.


It is not really possible to use this water for a pond or similar feature because it is not reliable and the pond would simply empty.

The only solution is drainage into a soakaway since you have no outlet into a stream or ditch for drainage water. More on this on:


Wet corner of lawn

Posted On: January 13, 2010

We have a lawn at the back of our house, and one corner can be very wet in winter and spring. Are there plants that i can put in, to soak the water? i want low lying plants that will not block our view from the back window in our kitchen. the area is about 10ft by 5ft approx. i thought about a small pond but the area is too small.


You could either drain it by digging a soakaway to get the water down fromt he surface or treat it as a bog garden with plants that like wet ground, but it must not dry out too much in summer. Suitable plants include: candelabra primulas, ligularia, certain irises, mimulus, peltiphyllum, gunnera, loosestrife, lysimachia, sedges and lysichiton.

But it is quite a small area and will not accept many plants, some irises and primulas might be enough.

oddment of part of pond liner needed

, greystones Posted On: December 19, 2009

I have one large half barrel which i want to make into a barrel pond, where can i get an oddment of pond liner for this, i am on a disability pension and never could afford a massive piece for this one feature. Thanks in anticipation.


You can use any kind of polythene sheeting for this purpose as it will be supported and protected by the sides of the barrel.

Butyl vs. pvc pond liners

, Templeorum Posted On: April 20, 2009

My pond has been dug and now ready for a liner… dimensions are 16ft x 11ft and 3 ft deep. Do you have a recommendation butyl vs. pvc. Have installed butyl in a Wicklow pond but is it really that much better than modern pvc 2mm thick?


Butyl rubber, or synthetic rubber, or IPDM liner .... all the same thing are more expensive than other liners but more durable and longer lasting. Still worth the extra money.

More on ponds at:



Problem with small pond

, Blessington Posted On: March 24, 2009

My small pond 5ft. by 2.5ft.and 18″ deep has become muddy and slimey. The slime adheres to the plants (oxygenater, Lilly and Iris) and also floats in lumps on the surface. There were fish in it up to 5 months ago when the heron got them all. It is generally very muddy and disgusting. I have a filter in it but have switched it off for the moment. Should I empty it and start again or is there any treatment for it. Looking forward to hearing from you. Thank you.


A pond of 5 x 2 x 1.5 feet in size tends to be tricky because it heats up easily and pollutes easily.

The thing to realise about fish is that they excrete nutrients into the water and this encourages algae. If you want fish you must have a good UV filter and, ideally, a bio-filter as well to break down their waste.

Don't bother emptying the water. Put in a 5cm layer of gravel with some soil mixed ... this helps to create a natural cycle, but a small body of water can overheat and produce a lot of algae, although this will settle down.

Can I have a pond without pump and filters

, Foxford Posted On: June 18, 2008

I am in the process of creating a wildlife garden pond. Rough dimensions are 60ftx30ft with average depth of 4ft. I want to be as enviromentally friendly as possible and would like to avoid additional energy use (electricity for pump for water circulation and filtering). Is it possible to do this without the water becomming stagnant and preventing the growth of algae – could bales of straw do the trick? Are there any other ways I could deal with with water circulation such as tap water from well or rainwater diverted from roof? Any advice appreciated.

It is very easy to divert roof water into a pond and it will help to keep it fresh. There is no need for pumps etc  Top up the pond if it gets very low in level. Normally a roof-replenished pond will not drop by more than about 10cm in level in a normal summer.

The roof will provide too much water occasionally and an overflow might be needed, or simply allow the pond to overflow its banks. The water seeps away to surrounding soil.


removal of blanket weed

, Howth Posted On: March 28, 2008

Do you have any suggestion, please, for the removal of blanket weed in a pond? There are fish in it. I have been doing it manually but with very limited success. Many thanks

Blanket weed is a filamentous alga, which accounts for the long trails of green. The principle is that if want water to stay clear, it must be low in nutrients so that algae cannot grow. But if you feed fish, and they pass out nuntrients in their waste, the nutrients levels do not fall as they normally do naturally.

If you want have fish and clear water, you probably need to install a UV-filter to kill the algae and a biological filter to use up the nutrients. You can also plant lots of water plants, any kind, because they compete for the nutrients, and they also shade the water, reducing algal growth.

Jabbing the trails of blanket weed with a long cane, split at the end and twirling it can get rid of large amounts quite quickly, but will have to be repeated until the problem with excessive nutrients is solved.