Domakihub How to Use Pool Algaecide and Keep Your Water Clear
A step-by-step guide to applying algaecide correctly so your pool stays algae-free all season.
Reviewed by Domakihub pool pros · 2026-06-23 · 4 min read
Algae can turn a sparkling pool cloudy and green within days, especially in the Greek summer heat — a serious problem for homes, holiday rentals, and hotel pools that need to look their best at all times. The video above from Swim University cuts through common myths about algaecide and shows you when and how it actually works. This guide takes those lessons and gives you a clear, ordered process you can follow yourself, or hand to your pool technician.
What Algaecide Actually Does
Algaecide is a chemical treatment designed to kill or prevent algae growth in pool water. It works alongside chlorine rather than replacing it — think of chlorine as the primary weapon and algaecide as a preventive shield that stops algae from taking hold in the first place.
Most residential and rental pools in Greece benefit most from a weekly preventive dose added during routine maintenance, rather than waiting until the water has already turned green. Once a full algae bloom appears, you will need shock treatment first; algaecide alone is not enough to clear heavily infested water.
Choosing the Right Type
There are three main types: quaternary ammonium (quat) algaecides, which are the most common and affordable; polyquat (polyquaternary ammonium) algaecides, which are foam-free and gentler on the water; and copper-based algaecides, which are potent against black algae but can stain pool surfaces if not dosed carefully.
For most pools in Greece — especially those with light-coloured tiles or marble finishes common in holiday villas — a polyquat 60 product is the safest all-rounder. Copper-based products should only be used when dealing with persistent black or mustard algae, and always with extra caution around the pool surface.
How to Apply Pool Algaecide: 5 Steps
- 1
Balance your water chemistry first
Before adding any algaecide, test your pool water and bring pH to 7.2–7.6 and chlorine to 1–3 ppm. Algaecide works far less effectively in unbalanced water, and adding it to a pool with low chlorine or wildly off pH is a waste of product and money.
- 2
Calculate the correct dose
Read the product label and calculate the dose based on your pool's volume in cubic metres (1 m³ = 1,000 litres). Most polyquat products call for roughly 60 ml per 10,000 litres for a preventive weekly dose, and up to double that for a treatment dose. Never guess — overdosing a quat product causes persistent foam.
- 3
Dilute and distribute around the pool perimeter
Pour the measured algaecide into a clean plastic bucket and add several litres of pool water to dilute it. Walk slowly around the pool and pour the diluted mixture close to the water surface along the perimeter, rather than dumping it all in one spot. Even distribution is essential for even protection.
- 4
Run the pump for at least 8 hours
Switch on the circulation pump immediately after adding algaecide and let it run for a minimum of 8 hours, ideally overnight. The pump distributes the product through every part of the pool including the dead spots near steps and behind ladders where algae typically starts.
- 5
Brush pool surfaces and repeat weekly
On the day after treatment, brush the walls, floor, and any shaded corners with a pool brush. This dislodges any early-stage algae spores before they can anchor. For ongoing prevention, add a maintenance dose of algaecide once per week, ideally on the same day as your weekly shock treatment but added several hours apart.
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FAQ
- Can I swim immediately after adding algaecide?
- With most polyquat algaecides you can re-enter the pool after 15–30 minutes once the product is fully circulated, but always check the specific product label. Copper-based algaecides typically require a longer wait of several hours. When in doubt, run the pump for at least one full circulation cycle before swimming.
- My pool is already green — will algaecide fix it?
- Not on its own. A green pool has an established algae bloom that requires shock treatment (a high-dose chlorine or non-chlorine shock) first. Once you have shocked the pool and the water starts to clear, then add algaecide as a follow-up to kill off remaining algae and prevent regrowth. Skipping the shock step means the algaecide cannot keep up.
- How often should I add algaecide to my pool?
- For most residential and rental pools, a preventive dose once per week is sufficient throughout the swimming season. In very hot conditions (above 35 °C) or after heavy rain and high bather loads — common in Greek summer — you may want to increase to twice weekly. If the pool sits unused for more than a week, add a full maintenance dose before reopening.