There’s nothing quite like basking in the sun and enjoying your backyard pool. However, green pool water due to algae growth can quickly ruin the fun. In this article, we’ll discuss the causes of pool algae and how to eliminate them, ensuring a safe and enjoyable swimming experience.

Understanding Algae in Pools

Algae are photosynthetic organisms that produce their own food using sunlight, water, and carbon dioxide. They can float in the water or cling to your pool’s walls, floor, or stairs. It’s essential to treat algae as soon as possible because they can grow rapidly and reproduce, potentially harboring dangerous pathogens like salmonella, parasites, or E. coli.

Poor filtration, imbalanced water chemistry, inconsistent or low chlorine levels, and inadequate water circulation can all contribute to pool algae growth.

Identifying the Causes of Algae Growth

Algae spores are present everywhere and can enter your pool through wind, soil, or rain. Issues arise when these spores multiply in your pool’s water, forming algae blooms or growing on your pool’s surfaces. Factors that promote algae growth include low chlorine levels, imbalanced pH, dirty filters, or poor pool circulation. Swimwear or toys used in natural bodies of water with algae can also spread spores.

Neglected swimming pool with debris and algae

Preventing algae growth is much easier than dealing with an existing problem, so it’s crucial to maintain a proper pH balance, clean your filtration system, and wash off any items exposed to natural water sources.

Types of Pool Algae

  • Green pool algae: The most common and easiest to eliminate, green algae can quickly cloud your pool water and leave green slime on surfaces.
  • Yellow pool algae: Also known as mustard or brown algae, this type is more prevalent in humid regions and appears as pollen or sand-like deposits on your pool’s shady edges. It is chlorine-resistant and requires multiple cleaning and shocking treatments to remove.
  • Black pool algae: This type is caused by bacteria, not algae, and is challenging to eradicate due to its roots anchoring into solid surfaces. Black algae require thorough removal over several cleaning sessions, or it will quickly reappear.

How to Remove Algae from Your Pool

Dirty swimming pool water
  1. Clean filters frequently: Monitor filter pressure and clean the filter media regularly to maintain optimal performance. Backwash sand or DE (Diatomaceous Earth) filters, and spray cartridge filters to clean them.
  2. Brush pool walls and floor: Use a sturdy pool brush on a pole to remove algae from surfaces, focusing on tight spaces and corners where algae thrive. For concrete or gunite pools, use a stainless steel bristle brush; for other materials, use a nylon bristle brush.
  3. Test and balance water: Use test strips, a digital kit, or a liquid test kit to check your pool’s alkalinity and pH, ensuring that your sanitizer will work effectively against algae.
  4. Shock your pool: Apply a calcium hypochlorite shock to super-chlorinate your pool water and prevent algae growth. Double, triple, or quadruple the recommended dosage based on the type of algae and the size of your pool. Always shock your pool at night or dusk to avoid losing chlorine to sunlight.
  5. Use a pool algaecide: Apply algaecides to destroy algae and prevent regrowth, but be mindful of the potential for high costs and metal-based formulations that could discolor your pool water.

Preventing Pool Algae Growth

A home swimming pool that has turned dark green from neglect
  • Test and balance your water weekly, after storms, or following heavy use.
  • Run your pump for 8-12 hours daily, and shock your pool once a week during peak swimming season.
  • Clean or backwash your filter regularly.
  • Wash and sanitize all pool equipment, floats, and toys before reintroducing them to the pool.
  • Apply flocculant or algaecide immediately upon noticing the beginning of algae growth.

Final Thoughts

Green algae are the easiest to remove from your pool, but it’s important to address them as soon as they appear, as they can harbor dangerous bacteria and multiply rapidly. Mustard and black algae are more challenging to eliminate, with black algae being a type of bacteria rather than true algae. Use the information provided in this article to help you tackle your algae problems and enjoy a clean, clear swimming pool all season long.