How to Remove Black Algae in My Brighton East Pool?

Author : Same Day Pool Cleaning | Published On : 22 Jun 2026

If you've noticed dark, almost black spots appearing on the walls or floor of your pool that don't brush away easily, you're most likely dealing with black algae, and it's one of the most stubborn pool problems a homeowner can face. Unlike the green algae that turns pool water cloudy and clears up relatively quickly with the right chemicals, black algae is a different beast entirely. It forms in layers, develops a protective outer coating that shields it from chlorine, and anchors itself into the surface of your pool with root-like structures that penetrate deep into plaster, grout lines, and concrete. Simply shocking the pool or adding extra chlorine rarely gets rid of it completely, and without the right approach it almost always comes back.

Understanding Why Black Algae Is So Difficult to Treat

Black algae isn't actually a true algae in the traditional sense. It's a type of cyanobacteria, and its biological structure is part of what makes it so hard to eliminate. The outer waxy layer it develops acts as a natural barrier against chemicals, meaning that even well-maintained pools with healthy chlorine levels can harbour black algae growth once it takes hold. It thrives in areas with poor circulation, rough surfaces where it can grip, and in spots that don't get regular brushing. Shaded corners, steps, and the waterline are common hotspots. Because it embeds itself into porous surfaces rather than just sitting on top of them, killing the visible growth without addressing the roots simply causes it to regrow within weeks, which is why so many pool owners find themselves fighting the same patches repeatedly throughout the season.

The Right Approach to Getting Rid of It

Treating black algae properly takes more than a single chemical treatment. The most effective approach starts with aggressive brushing using a stainless steel brush on plaster pools or a hard nylon brush on fibreglass surfaces, which breaks through that protective outer layer and exposes the organism to the chemicals you apply. Directly applying a chlorine tablet or granules to the affected spots after brushing gives the treatment the best chance of penetrating to the roots. A pool shock treatment at a higher than usual dose, combined with running the filter continuously for at least 24 hours, helps clear any remaining bacteria from the water itself. Stabilised chlorine levels above the normal maintenance range are usually needed for several days after treatment to ensure the algae doesn't regrow. For pool owners around the area, finding professional help with Pool Cleaning Brighton East is often the most reliable way to ensure the treatment is done properly the first time, rather than going through repeated cycles of partial treatment and regrowth.

"We'd been battling black spots in our pool for the better part of two summers and nothing we tried seemed to get rid of them for good. We'd scrub them back and within a few weeks they'd be creeping across the steps again. A neighbour suggested we call Same Day Pool Cleaning and it was genuinely one of the better decisions we've made for the house. The team came out, explained exactly what we were dealing with and why our previous attempts hadn't stuck, and carried out a proper treatment that actually got to the root of the problem. It's been several months now and we haven't seen a single spot return. The pool looks better than it has in years and we finally feel confident having people over for a swim."
— Marcus and Jenny L., Brighton East

Why the Problem Keeps Coming Back After Treatment

One of the most common frustrations pool owners have with black algae is that it appears to clear up, only to return weeks or months later. This happens when the treatment addresses the surface growth but doesn't eliminate the root structures embedded in the pool surface. Incomplete brushing before chemical application is often the reason, since the protective layer needs to be fully broken before any chemical can reach deep enough to matter. Poor water circulation also allows black algae to re-establish itself in low-flow areas even after treatment, so checking that all return jets are properly positioned and that the pump is running for adequate hours each day is an important part of preventing recurrence. In fibreglass pools, any surface damage or crazing gives black algae additional grip, and those areas may need to be assessed and addressed as part of a longer-term prevention strategy.

Preventing Black Algae From Taking Hold Again

Once black algae has been successfully eliminated, consistent maintenance is the most effective way to stop it returning. Regular brushing of pool walls and floors, even when the water looks clean, disrupts any early-stage growth before it has a chance to establish itself. Keeping chlorine levels stable rather than allowing them to fluctuate significantly reduces the window for bacteria to take hold. Cleaning and inspecting pool filters regularly ensures that water is circulating effectively through every part of the pool. After heavy rainfall or a period of high bather load, a preventative shock treatment is a sensible precaution, particularly through the warmer months when algae growth accelerates.

Getting Your Pool Clean and Keeping It That Way

In conclusion, black algae is one of the more challenging pool problems to deal with precisely because its biology makes it resistant to the usual chlorine-based treatments that work well on other types of algae. Tackling it properly requires thorough brushing to break its protective coating, targeted chemical application, a high-dose shock treatment, and sustained elevated chlorine levels over several days. Without each of these steps working together, partial treatment leads to the familiar cycle of apparent clearance followed by regrowth. Same Day Pool Cleaning can take on the full treatment process with the right tools and chemical knowledge to ensure black algae is properly eliminated rather than temporarily suppressed, and help you put a maintenance routine in place that keeps your Brighton East pool clean, clear, and genuinely enjoyable to use all season long.