We should not really speak of “fighting” algae since algae are as much part of a pond or pool as plankton and aquatic plants. A pool without algae is just as unhealthy as one with too much. But keeping algae in their proper bounds is rather difficult, so the word “fight” is rather apt after all.
The reason for excessive algae growth is always an overload of nutrients accompanied by oxygen depletion a sign that something is out of kilter. As with all troubles, prevention is better than even the best cure. That is why, if you want to avoid algae problems, you should follow all of the succeeding recommendations. Following just one of them will not produce the desired results.
Plants: Make sure you plant your pool properly. Plants draw nutrients from the water and thus largely deprive algae of food. Especially submerged plants, such as water-weed and pondweed, clearly inhibit algae growth because they compete for the same food. But floating plants, like duckweed, and plants with floating leaves, like water smartweed, also discourage algae. Since algae grow faster in warmer water, plants that shade the water, such as water lilies, floating heart, and other plants with floating leaves, are good allies because they keep the water temperature down.
Snails: Introduce some snails (for example Lymnaea stagnalis, Ancylus, Paludina vivipara, Planorbis corneus). They feed on algae, dead plant parts, animal wastes, and floating debris. Generally, snail populations do not get out of hand; however, in pools with fish you have to watch out that no fish food drifts to the bottom. This extra bonanza would be gobbled up by the snails, which would then reproduce at a greater rate.
Building and Maintaining the Pool: In pool construction and maintenance is where you can do the most good, both in the initial stage and later on throughout the year:
- Construct the pool’s edge in such a way that even during the heaviest downpours no fertilizer is washed into the pool from the lawn or the garden.
- Check the pH of the pool water periodically. It should be between 6 and 7.5. If necessary, add humic acid (available in extract form at pet or aquarium stores) or hang bags of peat (without added fertilizer!) in the water until the proper condition is reached.
- See to it that the water is aerated enough and there is a sufficient oxygen supply throughout the year. An air pump can be kept running all year.
- If you keep fish in your pool, good filtration is of the essence. Either install a special pool filter or set up a stream to function as a biological filter.
- Periodically remove visible algae, long strands of algae, and tuft like formations by hand or with a skimming net.
Improper Measures: Do not use any chemical agents to get rid of algae. These products contain poisons that harm all pool life and get rid of the algae problem only temporarily. After a short time the algae will start growing again, and you are back where you started from.