Concrete Pond Construction

Q. I intend to have a skimmer and have the return through a venturi on the opposite side of the pond. This will be driven by an external Aquamax 5500 pump. Does it make any difference whether the pump is situated closer to the skimmer or closer to the venturi side?

A.It does not really make a lot of difference. Most people place the pump in the pump room after the filter so this usually means the pump is closer to the venturi. In theory the pump should be as close as possible to the skimmer, but in most cases this is not convienient.

Q. Does the main return to the pond come in at 90 deg to the pond wall or is it better to make it go into the wall at 45 deg?

A. It is normal to bring the main return to the pond for the venturi some 4 to six inches below the water level. You can then add a 45 degree bend to the pipe without using solvent and this allows you to alter the flow of the water.

Q. I was wondering about pond power skimmers. How long should one be kept on for? Is it better to use a timer? What kind would you recomend for a pond 15ft by13ft 4ft?

A. The length of time running each day depends on your own requirements, and will depend on the amount of debris and leaves that get on the surface.
An average time is a couple of hours twice a day. You may want to change it at different times of the year.
Many of our members do have it connected to a timer, and arrange it to be running before they return home from work.
Any type of swimming pool skimmer is OK, as the pump is the important part. Ideally it should be at least 1,800 to 2,000 gph.

Q. I am thinking of fitting a power skimmer, although I've no idea how much they are.

A. The skimmer itself without pipework or pump is £65. (UK prices 2001) I would definitely fit one of these even if you do not connect it up until later. You cannot add it to a pond once it is built. They keep the surface very clear and make the water look much better. A must in my opinion.

Q. I intend to fit a power skimmer because I have a problem with many trees around. How strong has the pump to be so that it can work efficiently?

A. The pump has to be big enough to draw in water from the surface of the pond so that the floating debris is drawn into the skimmer basket.
The minimum size of the pump should be about 1,400 to 1,800 galls/hr for your pond. Some members do use a swimming pool pump for this as they are really powerful. As they are usually only used for a few hours a day then the cost of electricity consumed is not really important.

Q. You recommend a pretty high pumping rate for a power skimmer which is fair enough, but how would that perform in a small(ish) pond such as mine? I feel that it would be too much of a tidal wave! What if (hypothetically) I were to plumb in my skimmer into the pipework from the bottom drain? Or are non power skimmers not very effective?

A. For a power skimmer to work effectively they have to have a good suction so that they draw in the debris over a large area. I consider that the pump must be at least 1,400 gals/hr to do this. You have the additional cost of buying another pump, but the electricity cost is not very high as you only use it a couple of times a day. If you prefer you can fit the skimmer into the wall and connect it up later. You connect the outlet to the pond with a venturi and as this is below the surface all it will do is cause a current which is good as it makes the fish swim against it. A tidal wave is an exaggeration and will not happen. Mine is connected to the waterfall. If you plumb into the bottom drain you are reducing the amount of water being drawn from the bottom drain, but it would work. I personally would not advise doing it that way.

Q. Does a skimmer reduce the chance of getting surface foam (from protein waste I believe?). I would have thought that a venturi return would have the same effect as stirring up the washing up water after putting in your liquid.

A. If there is surface foam on the pond surface then this seems to disappear when the skimmer is switched on. I have not seen the problem you are talking about.

Q. Is it possible to fit some type of surface skimmer to a 4,000 gallon pond with two feet built out of the ground (total depth 5ft) without having to disturb the outer brickwork which is reclaimed old brick which would not stand too much work on it.

A. If you are not able to make any hole in the side of the pond, and most of us would not wish to, then you have to pump this out, and a solution that could solve your problem is an article on power skimmer in "Hints & Tips".

Q. Can you give me any ideas for a 3" gravity skimmer?

A. To have a three inch gravity skimmer you need a length of three inch pipe through the wall of the pond then inside the pond fit a 90 degree bend to this. You then need a vertical pipe to just below the surface of the pond preferably fitted with an adjustable top so you can adjust the height. The other end of the pipe is run to the settlement chamber or the vortex chamber. To make this work the filters must be gravity fed as they will then operate at a depth slightly below the pond level and so this allows the water to flow.

Q. I am building a new pool and wish to use a floating skimmer, can anyone recommend one, as there are several available.

A. If you are building a new pond with a liner I would recommend you use an in wall skimmer as these are much better than a floating skimmer.

Q. This is my first year using aeration in my pond and filter, the weather forecast for the next few days is for lower daytime tempatures and for frost at night. I,m wondering should I switch off my pump at this time or gradually reduce the air in the filters as I,m worried that a sudden shut off would somehow be a shock to the filters and maybe dangerous? Have I got it right or am I being too cautious and if it is to be gradual, what kind of timeframe?

A. You do not say what type of media you are using in the filter.
With Kaldnes K1 or Japanese matting then the air pump must never be shut off.
If you are using aeration with other type of media then it is still advisable to keep it running during the winter.
Any air stones used in the pond during the summer months can be removed assuming you have sufficient aeration from other sources such as a venturi.
The ideal way is to have the air pump in a shed or something similar. Do not put it in a greenhouse as it might pick up some dangerous chemicals that might be in the air.
If this is not practical in your case then some people build a small housing to go over the pump in a shape like a small dog kennel which can be easily lifted up to service the pump. Make sure that plenty of air can get in, but as the pump runs quite warm it will take some of the chill off the air going into the pump.
Some people put the air pump down in their pump chamber. With a gravity fed filter this will be below the surface of the pond water. It will be necessary to fit a non return valve which can be purchased for this use, but they are not 100% reliable.