Antifouling Paint Alternatives. Bottom Paint No More!

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The ocean is vast. In fact, many experts suggest that we know more about outer space than we do the depths of our own oceans. Modern imaging and submarine technology have allowed us to touch the tip of the iceberg, and every day new species of plant and marine life are found in the ocean. 

While humans have dominated the land, the ocean is probably the one place on our planet’s surface we’ll never fully control or understand. Our boats may be giant to us, but to the ocean, they’re just another foreign object passing through. 

It’s no wonder, then that since the first boat was launched in ancient times, sailors and mariners have complained about “hull fouling.” 

Our answer to hull fouling has long been to use antifouling paints (aka ablative paints), commonly containing toxic chemicals, frequently copper. They work, but adding toxic chemicals to the ocean is a no-no! And in many areas, there are attempts to ban these paints.

This is where Antifouling paint alternatives come in. There several innovations in the hull-protection space, and in this article, we’ll look at a few popular ones.


Hull Fouling

Fouled Boat Hull

Marine life has a resilience that’s found few other places on earth, and in the vast blue sea where coral reefs and rocks are nowhere to be found- our boat’s hull makes the perfect home for small aquatic life. 

While this may sound cute at first, every old salt who knows better will give you an hour-long rant about how much they hate it. 

Boats are similar to airplanes in the fact that they operate on a singular principle to maintain their high speeds and efficient fuel usage (important when you’re miles in the air or out at sea, far from any refuel post)- low friction and drag

Marine build-up is bad for two key reasons:

  • It increases friction and drag. 
  • It can eventually cause damage to your hull. 

The first point is an obvious one. Large barnacles and plants growing on the bottom of your boat reduce the aerodynamic profile of your otherwise sleek hull, reducing your speed and fuel efficiency by as much as 20% in more extreme situations. Even a 10% reduction in fuel efficiency is enough to cost most yacht or ship owners an arm and a leg in fuel costs!

As for hull damage, this can take a while to appear, but trust that it eventually will. While ship hulls are designed to withstand a lot, hull fouling can slowly eat away at the protective coating, exposing the bare metal to saltwater. This quickly leads to rust and corrosion- a problem that can absolutely cripple ships and require extensive welding to repair. 

This was often a problem in old-fashioned wood ships as well. While they didn’t have to worry about rust, the marine hitchhikers would often feed on the wood, turning it into a soft substrate for more seeds and plant life to grow. This would eventually lead to holes in the ship and possibly cause it to flood or sink. 

Check that bilge pump!

In today’s article, we’re going to be talking about marine build-up, commonly known as hull fouling, and the various methods that you can use to clean it and prevent it in the future so that your ship can operate safely at maximum efficiency. 

Most Common Types of Marine Fouling

Marine hull fouling is typically broken down into two sub-categories: 

  • Microfouling
  • Macrofouling

Microfouling refers to microscopic organisms that are usually the first to hitch a ride. 

Macrofouling refers to larger, more visible organisms that come secondary- usually to feed on the various micro-organisms.
We’ll discuss both in-depth. 

What Causes Marine Build-Up? 

Now, one may think that the underside of a hull is a harsh environment for life to thrive, but marine life, in particular, thrives in what we think of as “harsh.” Compared to the extreme pressure, darkness, and depths of the ocean floor, the bottom of a boat is like a 5-star resort for small plants and critters who enjoy the warmer water temperature and close proximity to surface-level sunlight. 

Below, we’re going to take a look at the complete process of hull fouling from start to finish. 


Boat Hull Algae


Algae is one of the most abundant organisms on the face of the planet and grows almost anywhere there is water. It can latch onto anything and survive in most natural environments as long as the water pH is relatively familiar.

Although it thrives especially well in more stagnant conditions such as ponds, lakes, or harbors (usually where your boat picks it up in the first place), it can survive just fine on the underside of your hull as long as it has a solid surface to grab onto. 

The first sign of boat fouling is a greenish-black, slimy-feeling residue on the bottom of your boat- this is the algae. If this is all you have, then you’re still in the early stages and the problem is a lot easier to fix and prevent in the futre. 

Microscopic Organisms

Algae is one of the most common forms of plant life in the ocean and it’s also one of the most common foods. Small organisms are attracted to this algae as it’s an abundant food source. Also, the hull of the ship gives them relative safety as they’re not aimlessly drifting through the ocean.

Once they make a home, these organisms usually reproduce and multiply across the bottom of your hull. 



Algae build-up creates an easy-to-grip surface for some of the most popular shipyard organisms- barnacles. Barnacles start off as small almost microscopic organisms drifting through the ocean until they find a solid surface to attach themselves to.

While ships and docks are the most common, they’ve even been found attached to large marine animals such as whales and sharks. 

Once barnacles come into contact with the bottom of your hull, they secrete a glue-like substance that allows them to firmly grip onto the hull. This is what makes them so hard to remove! Apart from having a safe space to rest, barnacles are filter feeders and love the close proximity to algae and other micro-organisms that they can feed on. 


Once enough algae, micro-organisms, and barnacles give the hull a rough underside, drifting plant seeds can easily get caught in the mixture and use it as a substrate to grow in.

A constant supply of nutrients and close proximity to sun rays make the underside of a boat particularly great for kelp to set seed and grow. 

Small Marine Life

Once the kelp comes, filter fish and other small marine life also turn the bottom of your hull into a home thanks to the safety provided in the shadow of the hull and the neverending food supply courtesy of micro-organisms and kelp- their two main food sources. 

Best Ways To Remove Marine Debris

As you can see, if you leave your boat unattended for too long, it can easily turn into its own self-sustaining coral reef ecosystem. This is why it’s important to clean your boat whenever possible and try to avoid leaving it in the water for extended periods of time. 

That being said, this isn’t always a viable solution for many boat owners, especially for those who have larger boats such as small freighters, fishing boats, or large pontoons that rarely get taken out of the water for a proper hull cleaning. 

Unfortunately, to completely remove all of the debris, you’re going to have to remove it from the water first. Once you clean it, then there are numerous options for keeping marine debris away in the future. First, though, you must clean the old build-up. 

Below, we’ll discuss the top ways to remove marine fouling so that you can start fresh with a clean slate. 

Pressure Washing

Pressure Washer

No matter how little or much hull fouling you have when you take the boat out of the water, your first step is going to be hitting it with a pressure washer. If possible, use one of the strongest machines you can. A machine that has an output of 5gpm (gallons-per-minute) or more will usually do the trick. 

Then, start with a jet nozzle and use it to remove as many of the large barnacles at a time as you can. It won’t get everything, but it should knock off a good bit of them. Secondly, you’ll want to switch to a wider fan-type nozzle and get a little bit closer to the hull. This will help to remove a lot of the sticky algae and plant life. 

It may take a while, but it’s an important part of the process. 

Hull Scraping

Paint Scraper

Once you’ve gotten as much done with the pressure washer as you can, then it’s time to move on to hull scraping. This is going to be the most labor-intensive part of the process. You’ll need to take hard bristle brushes and some scraping tools and use them to vigorously clean and scrape any remaining barnacles and plant life off of the hull. 

While you should apply a solid amount of pressure, just make sure that you don’t overdo it and damage your hull. 

Acid or Calcium Wash

Starbrite Boat Wash

Once you’re finished with the hull scraping, there will likely still be some hardened glue-like residue leftover by the barnacles. After a few years of hardening, this material can be almost like concrete and can be very difficult to remove. Still, it creates drag, and if it’s not removed then it can be a great starting point for more hull fouling marine build-up in the future. So, while you’ve already got the boat out of the water, it’s best to go ahead and do everything at once. 

To remove the final layers of stubborn debris, the best thing you can do is to use an acid or calcium hull wash. This usually comes in a powder form that you’ll have to mix down with water, but sometimes it will come already pre-mixed.

Typically, the powder form tends to be a bit stronger and you can mix it down as powerfully as you want. 

This can usually be applied with your pressure washing by using an “X-Jet” tip that siphons the acid from a bucket into your pressure washer’s gun tip. If you don’t have this setup, you can purchase a standard hand-pump sprayer from your local hardware store for $20-$30 and mix your acid and water in here. 

Once mixed, coat all of the affected areas and let it sit (instructions vary depending on the acid brand you use). Then, crank your pressure washer back up and everything else should come right off! 

Preventing Marine Debris

Now, we’re going to get into how to prevent marine debris from building up in the first place! After all of the time you spent cleaning, you probably never want to do that again. Thanks to modern technology, you may not ever have to! 

How Anti-Fouling Paint Prevents Marine Debris

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One of the most common (and oldest) methods of preventing marine debris is to use one of the best anti-fouling paints. The TotalBoat Spartan shown above is a fine example. This not only gives your hull a new, refreshed appearance, but it also slows or completely prevents the growth of organisms and plants on the surface of your hull. Note that many standard bottom paints are not compatible with aluminum pontoons.

However, there is one problem regarding anti-fouling paint that commonly comes up. All of the most recent marine research says that almost all anti-fouling paint on the market is not only toxic on the hull itself but it can also poison the surrounding water.

As you can imagine, this is not only environmentally irresponsible, but it can be dangerous to people as well. Especially if you’re cruising around in areas where swimmers, surfers, and divers regularly frequent. 

Copper-Free Bottom Paints

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There are some antifouling paints on the market that don’t contain copper-based protectants. The above paint, which is TotalBoat Krypton, fits the bill. This paint does not contain any chemcials derived from copper, and is therefore at least somewhat more environmentally friendly than many other bottom paints.

The Krypton uses an organic biocide that is designed to be less harmful to the environment than copper paints, and is a decent alternative for those who simply don’t want copper-based paint.

TotalBoat Krypton Copper Free Antifouling – Marine Ablative Boat Bottom Paint | For Fiberglass, Wood, Aluminum & Steel Boats | Ideal for Outdrives & Trim Tabs (Red, Gallon), 1.00 Gallon (Pack of 1)
  • COPPER FREE FORMULA won't cause galvanic...
  • EASY TO APPLY: For brushing, use a...

Antifouling Paint Alternatives

Thankfully, there are several other more modern alternatives to anti-fouling paint that not only work better but also provide a long-term fix with minimal damage to the surrounding environment and waterways. 

Aurora VS721 Bottom Coat

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The cheapest solution is to apply a protective bottom coat to the hull like the Aurora VS721 shown above. It’s basically a clear liquid that prevents algae, barnacles, mussels, and other marine critters from latching on and making it their home.

For added convenience, you don’t even have to sand down or repaint your boat first! While this method does add a little bit of extra weight to the bottom of your boat, it’s negligible compared to the weight added by marine build-up. 

The best part about it is that once it’s dry- it’s 100% non-toxic, so you can cruise around waterways with confidence knowing that you’re not hurting people or animals. It essentially works by making the bottom of the hull so slippery that plants and barnacles can’t latch on.

This also has the nice added effect of making your boat incrementally faster in the water! 

This anti-fouling paint alternative bottom coat is sold by the gallon. And while it is a bit pricey, you don’t need a lot.

In fact, one gallon should be good for most smaller boats. It’s designed to last for years too, so you don’t have to worry about re-applying it all the time like you would with a more traditional anti-fouling paint. 

And we all know that applying the paint is a pain!

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NRG Marine Ultrasonic Anti-Fouling System

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If you’re looking for a more modern, more permanent solution, and you’ve got more money to throw around, then a super-high-tech ultrasonic anti-fouling system like this by NRG Marine may be great for you.

Essentially, this device features two electrode-like cups that can be wired into the hull. These produce a high-frequency sound wave underwater. This sound wave creates tons of microscopic bubbles and a pressure difference that makes it impossible for micro-organisms and algae to grow on the hull. 

Very cool!

These devices are 100% safe and non-toxic to animals and people. The ultrasonic effect only affects the area within a few inches of the hull so you’ll never have to worry about hurting surrounding wildlife or hurting your chances while fishing! 

NRG Marine is at the forefront of marine technological innovation. Their SoniHull Duo system, while a bit expensive, is worth every penny that you spend on it. This little device is built to last and can potentially save you tens of thousands of dollars in expensive coats, repaints, and cleaning throughout your boat’s life. 

It’s 100% quiet, will never disturb you or your passengers, and there’s no drilling necessary! If you’re familiar with wiring, all you need is a power source to hook it up to and you’re good to go. If not, you may need to have an electrician hook it up for you.

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Final Thoughts

Constantly cleaning, scraping, and repainting your hull with antifouling bottom paint is an arduous, tankless task. It’s a lot of work, and you can’t even really see it! The antifouling paint alternatives shown above are more environmentally friendly, and are creative solutions to hull fouling.

There is certainly more up-front expense to these compared to copper bottom paints, but when looked at over a decade+ of boating, the costs may end up evening out.

Happy boating!

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