If you have got green, slimy patches creeping across your patio, black speckled staining on your walls, or moss pushing up between your paving slabs, you have probably wondered whether a single product can really deal with all of it. It is one of the most common questions we get asked: does Patio Magic kill moss, does it get rid of black spot, and will it actually shift the algae that makes paths so slippery after rain? The honest answer is that moss, algae and black mould are three different organisms, and Patio Magic deals with each of them slightly differently. Understanding those differences will help you know exactly what to expect and when, rather than assuming the product has failed just because your patio does not look spotless the day after treatment.
Patio Magic! is made by Evergreen Garden Care UK Ltd, the same company behind Miracle-Gro and Levington, and its active ingredient is benzalkonium chloride, present at 5-10% w/w depending on the pack (the 2.5L concentrate label states 7.5% w/w, or 75g per litre). This is a biocide formulated specifically to kill green algae, moss and lichen on hard outdoor surfaces such as patios, driveways, paths, block paving, garden walls, garden furniture, greenhouse glass and decking. It is not a pressure washer replacement and it is not designed to physically scrub anything away. Instead, it works chemically, breaking down the organisms at a cellular level so that they die off and can eventually be brushed or washed away on their own.
How Patio Magic Works Against Moss, Algae and Black Spot
Because benzalkonium chloride is a broad-spectrum biocide rather than a targeted moss killer or a targeted algaecide, it attacks the cell structure of all three organisms once it is applied. The key thing to understand is that moss, algae and black mould do not have the same biological structure, so they do not die at the same speed. Green algae sits as a thin film on the surface, so the active ingredient reaches it almost immediately. Moss has rhizoids, root-like structures that anchor it into the surface and hold moisture, so it takes longer for the product to fully penetrate and shut the plant down. Black mould and the staining associated with it behave differently again, which we will come to below. This is why you should not expect uniform results across your whole patio on day one; different patches of growth will respond on their own timeline.
You do not need to rinse or scrub after application. Once Patio Magic has been applied to a dry surface, with no rain forecast for 5-6 hours, you simply leave it to work. The product breaks down naturally over time, and the dead growth is gradually washed away by rainfall or can be brushed off once it has fully died back.
Will Patio Magic Kill Moss on Your Patio?
Yes, Patio Magic is formulated to kill moss on patios, driveways, paths and block paving, but it is worth being realistic about the timescale. Because moss has that more established root-like structure compared with surface algae, it typically takes 1-2 weeks to fully die back and turn brown or black, at which point it can be brushed away. This is normal and is not a sign that the product has not worked; it simply reflects how moss is anchored into the surface compared with algae, which sits on top. If you are treating a patio with a heavy moss infestation, patience in that first week or two makes all the difference, and results are worth waiting for since a single application typically keeps the surface clear for several months afterwards.
For badly mossed areas, it is worth using the standard dilution rate for normal infestations, one part product to four parts water, rather than the lighter nine-to-one ratio, which is better reserved for surfaces with only light, early-stage growth. Both the 5L concentrate and the 2.5L concentrate can be diluted this way, and roughly one litre of diluted product covers 3-7m² depending on how porous the surface is and how heavy the growth.
Does Patio Magic Kill Algae?
Green algae is usually the fastest-responding of the three, and this is often where people see the most reassuring early results. Because algae sits as a thin surface film without the deeper anchoring structure that moss has, visible reduction typically happens within just 2-4 days of application. This is the slippery, slimy green coating you often see on shaded patios, north-facing paths, or areas that stay damp for long periods, and it is also one of the more hazardous growths underfoot, so getting on top of it quickly matters for safety as well as appearance.
If your main concern is algae on a large driveway or a big expanse of patio, the Ready To Use Spray is a convenient pre-mixed option that needs no dilution and covers up to 85m² straight from the bottle, which suits smaller or more occasional jobs where mixing a concentrate is not worth the effort. For bigger areas, the 5L concentrate covers up to 170m² once diluted, making it the more economical choice for driveways, large patios or multiple surfaces treated in one session.
Does Patio Magic Remove Black Spot and Black Mould?
This is where expectations need to be set carefully, because it is the question that causes the most confusion. Patio Magic's label confirms that it does kill black mould, so the organism causing those dark speckled patches on walls, render, roof tiles and paving is dealt with by the same active ingredient that tackles moss and algae. However, the staining and discoloration that black mould leaves behind can remain visible for a period even once the mould itself has been killed. In other words, the black spot you can see on the surface is often a cosmetic residue rather than an indication that the product has not worked. The mould organism is dead; what is left is staining, and that staining tends to fade and weather away gradually rather than disappearing overnight.
If you are treating garden walls or greenhouse glass for black spot, it helps to know this in advance so you are not disappointed by staining that lingers for a while after treatment. As with moss, patience is the key factor. Keep an eye on the treated area over the following weeks, and you should see the discoloration continue to lighten as the dead growth weathers away naturally.
How to Apply Patio Magic for Best Results
Getting the application right makes a real difference to how well and how quickly Patio Magic works. Always apply to a dry surface when no rain is forecast for at least 5-6 hours, giving the product time to start working before it risks being washed away. A watering can, pump sprayer or trigger spray all work well, and the aim is an even, thorough coating across the affected area rather than a light misting. For concentrate, remember the two dilution rates: one part product to four parts water for normal infestations, and one part to nine parts water for lighter growth. There is no need to scrub or rinse afterwards; simply leave the product to do its work and let rainfall or a light brush handle the dead growth once it has died back.
A few safety points are worth keeping in mind while you work. The concentrate can irritate skin and eyes, so wear gloves and eye protection when diluting and applying it, and keep children and pets off the treated surface until it is fully dry, which usually takes around 5-6 hours. Patio Magic is very toxic to aquatic life, so avoid letting runoff reach ponds, streams or drains, and try to avoid direct overspray onto nearby plants; if contact does happen, flush the area with water. The product works throughout the year, though it acts more slowly in cold weather, so autumn and winter treatments may simply take a little longer to show visible results than the same job done in warmer months.
What Patio Magic Will Not Do
It is worth being clear that Patio Magic is not marketed as a dedicated weedkiller, and it does not reliably kill grass or more established, embedded weeds growing in paving cracks and joints. If weeds alongside the moss and algae are part of your problem, treating them separately with a product like Doff Knockdown Path & Patio Weedkiller alongside your Patio Magic treatment will give you a more complete result. Used for what it is designed for, though, clearing green algae, moss and lichen, and killing off black mould, Patio Magic is a straightforward, effective option that needs no scrubbing or rinsing, just a dry day and a bit of patience while it does its work.
Whether you are dealing with a heavily shaded, algae-slick path, a mossy patio that has not been treated in years, or black speckled staining on a garden wall, choosing the right pack for the size of the job makes application easier. Browse the full Patio Magic range to find the concentrate or ready-to-use option that suits your patio, driveway or garden surfaces best.
