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When I was young I got swept up in the colloidal silver hype and even drank it for a while.
Then I decided it was probably not a good idea and stopped.
I don't recommend drinking colloidal silver, as its long term safety is an unknown variable.

Here are the components required.
A small plastic project case with a built in PP3 battery holder and a battery clip.
A couple of standard 4mm banana plugs as used on most test equipment.
A couple of matching sockets (one red and one black if desired).
An LED to indicate current flow, this should be a super high sensitivity LED like the modern Gallium Nitride green ones which will glow brightly at just a hundred micro-amps.
A resistor chosen to pass the desired current. In this case I used a 10K resistor for less than 1mA, but you could use a 1K resistor for closer to 10mA if you like.
And the most crucial bit, 2mm to 3mm diameter fine silver wire electrodes. The word "fine" defines that the silver is of extremely high purity and doesn't contain other metals like Sterling silver does.
You should be able to get the .999 (99.9% pure) silver at your local jewellery suppliers or bullion merchants, and while it is fairly expensive, it will last a long time.

First put a bit of masking tape on the base of the case to ease marking and drilling, then drill two holes for the electrode sockets (as shown above) and a 3mm hole for the LED in the middle of the front of the case.

Wire the guts as follows... The black battery lead goes to the negative electrode socket and the red battery lead goes to the anode of the LED.
The cathode of the LED (short lead) is connected to the resistor which is then connected to the positive electrode socket. This means that any current passing between the electrodes will cause the LED to glow while being limited by the resistor.
You may wish to file the tip of the LED flat without going too deep and damaging it's internal metalwork. This will improve the viewing angle. I've also used a small cable tie to secure the battery leads to the negative electrode socket to protect them from being pulled.
There's no switch because the unit only passes current if the electrodes are submerged in liquid. (Or laid on a conductive surface!)

Two pieces of the silver are cut to a length dictated by the depth of the glass tumbler this unit will be used with later. I cut mine at three inches (75mm).
Each piece of silver (a silver electrode) is then soldered into a banana plug.

The covers are screwed back onto the banana plugs, and the electrodes are ready.

A battery is fitted, the electrodes are plugged in, and the unit is placed on a glass of water with the electrodes submerged.
The LED should glow and after a while, a mist of silver will be seen forming around the anode. It may help to stir the water with the electrodes occasionally to diffuse the silver.
The amount of current flowing and the resultant intensity of the LED will vary according to the purity of the water. Ordinary tap water is pretty conductive because it already has impurities and minerals in it. Ideally you should use distilled water which is virtually impurity free, but doesn't conduct too well. In this case it may be better to design a system that operates at a much higher voltage.

As the trace quantities of silver merge into the water, it will become more and more conductive.

As the unit is used, a film builds up on the electrodes, and every so often it will be necessary to clean them by gently wiping them with either your fingers, or a soft nylon scouring pad.

Here's the unit in a hand to help get it's size into perspective. It's pretty compact.

You may want to experiment with colloidal copper too, which has similar effects as silver, but is reputed to be especially active against algae. For this you just need to make up another pair of electrodes with copper wire instead of silver. I can't say I was impressed at the copper version since it seems to be much slower than the silver.

You can do a bit of research on the Internet, searching for colloidal silver. It's quite a controversial subject and is surrounded with a lot of quackery as people try to justify excessive prices for what I've described above.

Something else to research is a pool ioniser, since this is a device that generally releases both copper and silver into pool water as described above. These devices can greatly reduce the need for chlorine in pools, and the scientific evidence of bacterial destruction is interesting.
Has lots of interesting information. They actually manufacture units for safe pool sterilisation.
This company sells a cute solar powered unit that floats on your pool and keeps it clean and fresh. The fact it's solar powered probably means it's useless here in the UK, but then we don't have many outdoor pools because the ice tends to rip our swimming trunks.
If you want to make pure colloidal silver, then you will need to use distilled water. While this is easily available in the USA, it's hard to find in the UK and the purchase of a water distiller will be required. Personally I think that tap water is fine for making a basic solution.

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