Solar Pool Fish

Solar pool fish are advertised as a low cost way to reduce evaporation from your pool and therefore help to keep it warmer. These little devices are certainly cheaper than a full solar blanket and come with no storage issues, but how do they work and how effective are they?

How Does It Work?

Information about the liquid inside the fish is very scarce, but from what little is available some conclusions can be reached. Let us consider what we are told about the liquid:

* It rises to the surface of the water and returns there quickly if disturbed. This tells us that it is not soluble in water which means that it is non-polar, like a hydrocarbon. Once at the surface it forms a continuous layer.

* It breaks down naturally and and is non toxic.

These three properties are typical of oils with small carbon chain lengths, like baby oil or olive oil. It is highly likely that the contents of the pool fish are either one of these substances or another oil that is very similar.

How Effective Is It?

If the oil is able to form a layer over the whole surface of the water there will be some reduction in evaporation. It is worth noting that this will only be the case when the air is still, as wind will push the thin oil layer around and it will not be able to maintain a continuous surface.

There is also the question of the thickness of the insulating layer. The oil molecules will themselves absorb heat from the water which they will then radiate to the air. While oil is definitely a better insulator than water, the thinness of the layer will keep the usefulness of this to a minimum.

In Summary

The solar pool fish is a low cost measure for pool owners who are on a low budget and want to have some immediate measure of insulation in place. However, the heat retention capacity of this thin oil film cannot compare with the effectiveness of a full solar blanket pool cover.