Any body of water needs to have contact with air in order for it to renew its oxygen as if it doesn’t, it will become over grown by algae. If a pond is not kept in contact with air, first the fish will start to die and as the algae at the bottom of the pond thrive, that algae will eventually take over the whole pond, transforming the beautiful pond into an eyesore which gives off an unpleasant odour. Of course, all ponds are in contact with air but unless an aeration system is fitted, only the water at the surface of the pond will be able to react with the air and soon that surface water will become absorbed by the oxygen lacking deeper waters. There are several aeration systems available to buy today and some are especially designed for shallower ponds, perhaps with a depth of no more than 6 feet whilst others, are specifically designed for use in deeper ponds. Fountains are a popular choice for a shallow pond as, as well as being able to provide aeration; they can also add beauty and elegance to the pond. Obviously the water that is thrown up by a fountain can come in contact with air and therefore become aerated by receiving oxygen but it is the fact that a fountain also creates a circulation in the water in the pond that makes it as efficient as it is. By circulating the pond’s water, a fountain ensures that all the water has a chance of being aerated and so keeps the pond looking fresh. In recent times, floating fountains have started to become popular as they allow for more variety in pond design, yet still ensure a pond is adequately aerated. Another aeration system or shallower ponds employ the use of propellers that churn up the water, allowing the water to be aerated in that way. As the propellers also create a circulation in the water of the pond, they too are efficient but only for the shallower ponds. The deeper ponds need to be aerated by using a diffusion system. The pond aerator fittings for a diffusion aeration system are a compressor, a diffusion unit and an air hose to connect the two. As the compressor is connected to a power source, it must not be placed in the water but can sit at the side of the pond. The diffusion unit though, must be placed in the water, at the bottom of the pond. As air is released by the diffusion unit, which it received from the compressor, the air will travel to the surface, allowing the water to react with it as it goes. As the air will have started at the bottom of the pond and travels to the surface, the water at all depths of the pond have the opportunity to react with it and draw oxygen from it, aerating all the water regardless of how deep that water may be.