Antifoul that works?

[LBD 224]

On 7/02/2026 at 6:33 AM, ex Elly said:

Altex No 5 Plus is now available. Right after we applied the old number 5 - drat!

https://www.smartmarine.co.nz/product/37657/no5-plus-antifouling?srsltid=AfmBOoqAfJ91JXZoLGRlPbC46rfKmP5ha-6MWzaCnw2_pnEiCc6WujRc

https://www.burnsco.co.nz/altex-no-5-plus-antifouling-4l?srsltid=AfmBOooa9Lcz9kcjZ5D60OOxGkrHNtdJNog_sfnh2pF4bKkPT19PrLBe

I just received an interesting reply regarding antifouling colours from Altex. 

I used the green standard #5 last bottom paint and it looks really nice, I then learned the #5 Plus is available in Green in Australia, but not in NZ... strange? I enquired why and was told.."With antifoul we are restricted by the government agencies that regulate this area the green Antifoul #5+ is an Australian formulation only and has only been authorised for sale in Australia. Unfortunately this product has not been approved for sale in New Zealand."

Does that mean the different colours are different formulation? How does one know which colour works best?

[Jonquil 549]

Bugger - I want green. Actually 2:1 green/white.....

[LBD 224]

4 minutes ago, Jonquil said:

Bugger - I want green. Actually 2:1 green/white.....

Light green would look nice on your gaffer..... Available standard #5 just not the plus version.

 

[motorb 58]

On 8/04/2026 at 11:57 AM, LBD said:

 

Does that mean the different colours are different formulation? How does one know which colour works best?

Yes. A few years back i had a tin of blue that was actually green, and it was the best antifoul Ive ever used. Altex refunded me, and once in the water, the paint below the waterline went pale blue after a few months.

A little birdie told me that was a faulty manufacturing batch with faaaar too much copper in it, which is what made it green.

So it wouldnt surprise me if sea green 5 plus is a superior product,  as I think ive already sampled a trial batch!

 

 

 

[Quattro 18]

I wonder if making copper fines and mixing in with AF would make any difference.   

[Psyche 941]

Pretty sure if it was that easy the paint companies would be all over it. 

[Frank 227]

I talked to the Altex rep a while back and he said that no 5 had a higher percentage of solids to resin than  most brands. 

AI reports that "Antifouling resins and binders are the engine of a marine coating, determining how effectively it releases biocides or prevents organisms from sticking to a hull. While the biocide (like copper) does the work of repelling growth, the antifouling paint binder system controls the rate of that release and the overall longevity of the protection."

I'm assuming there is a practical limit to the Solids vs Resin ratio, ie not enough resin means the coating performance is compromised despite being copper rich.

[Psyche 941]

Ever since ive had to antifoul boats there have been stories about improvements to AF paints with kitchen sink chemistry. Chilli powder, copper powder, copper sulphate, animal insecticides, anti fungal compounds, herbicides and so on. None have crossed the threshold into accepted regular use, there is a lot of confirmation bias, anecdotes etc and while i have no doubt some may work, for how long and at what cost? 

When paying anywhere from 250 to 600 dollars a can, its a bit risky to take a wild guess and add something into very expensive paint and risk degrading it.

I would need some serious proof or do my own test panels but I doubt I could do the paint chemists job better unless I fluked a magic ingredient. They have all the technology, materials and experience!

[Frank 227]

52 minutes ago, Psyche said:

Ever since ive had to antifoul boats there have been stories about improvements to AF paints with kitchen sink chemistry. Chilli powder, copper powder, copper sulphate, animal insecticides, anti fungal compounds, herbicides and so on. None have crossed the threshold into accepted regular use, there is a lot of confirmation bias, anecdotes etc and while i have no doubt some may work, for how long and at what cost? 

When paying anywhere from 250 to 600 dollars a can, its a bit risky to take a wild guess and add something into very expensive paint and risk degrading it.

I would need some serious proof or do my own test panels but I doubt I could do the paint chemists job better unless I fluked a magic ingredient. They have all the technology, materials and experience!

The Altex Rep said they had a list of Secret Sauce ingredients that folks swore by it was pinned to the wall in the lunchroom , from memory Cayenne Pepper, Round up, more copper powder,  Ivermectin (for de-worming the barnacles   etc etc 

[K4309 457]

2 hours ago, Psyche said:

Ever since ive had to antifoul boats there have been stories about improvements to AF paints with kitchen sink chemistry. Chilli powder, copper powder, copper sulphate, animal insecticides, anti fungal compounds, herbicides and so on. None have crossed the threshold into accepted regular use, there is a lot of confirmation bias, anecdotes etc and while i have no doubt some may work, for how long and at what cost? 

When paying anywhere from 250 to 600 dollars a can, its a bit risky to take a wild guess and add something into very expensive paint and risk degrading it.

I would need some serious proof or do my own test panels but I doubt I could do the paint chemists job better unless I fluked a magic ingredient. They have all the technology, materials and experience!

Agree with your sentiments, but I don't think it's people thinking they are smarter than industrial chemists, it's using compounds that industrial chemists aren't allowed to use, regarding all the govt regulations. There are plenty of compounds / AF that work, we just aren't allowed to use them (and in several cases for good reason).

And I doubt any readily available household items would work. So, the scenario then becomes one where people are deliberately using effective but highly toxic banned compounds. Just getting hold of that stuff is going to be an achievement in itself, given it's all highly controlled and impossible to import etc, etc.

Then, if someone does get something to work, they are knowingly going against regulations and would have had to have put a fair bit of effort into it. I suspect those people are then not going to advertise widely that they are breaking multiple regulations and potentially laws and expose themselves to prosecution, and possibly being criticised by the wider boating community, who tend to want to protect the environment, or at least not want to put nasty toxic compounds into it.

Like the stories you hear of people getting a secret supply of tri-butyl-tin based AF, something from a commercial shipyard or a drum of magic that fell off the back of a truck at the Devonport navy yard. Not that I've heard those sorts of stories recently.

But it is certainly incredibly frustrating when boaties are criticised for spreading all manner of invasive species (which were never anything to do with us) yet it's impossible to keep your hull clean and there are zero effective AF's available.

[Psyche 941]

If it works it must be bad for the environment therefore ban it, but hang on a minute it only works if it is bad for the environment LOL!!!

[Frank 227]

7 hours ago, K4309 said:

Agree with your sentiments, but I don't think it's people thinking they are smarter than industrial chemists, it's using compounds that industrial chemists aren't allowed to use, regarding all the govt regulations. There are plenty of compounds / AF that work, we just aren't allowed to use them (and in several cases for good reason).

And I doubt any readily available household items would work. So, the scenario then becomes one where people are deliberately using effective but highly toxic banned compounds. Just getting hold of that stuff is going to be an achievement in itself, given it's all highly controlled and impossible to import etc, etc.

Then, if someone does get something to work, they are knowingly going against regulations and would have had to have put a fair bit of effort into it. I suspect those people are then not going to advertise widely that they are breaking multiple regulations and potentially laws and expose themselves to prosecution, and possibly being criticised by the wider boating community, who tend to want to protect the environment, or at least not want to put nasty toxic compounds into it.

Like the stories you hear of people getting a secret supply of tri-butyl-tin based AF, something from a commercial shipyard or a drum of magic that fell off the back of a truck at the Devonport navy yard. Not that I've heard those sorts of stories recently.

But it is certainly incredibly frustrating when boaties are criticised for spreading all manner of invasive species (which were never anything to do with us) yet it's impossible to keep your hull clean and there are zero effective AF's available.

Although I'm highly skeptical I cant truthfully say that DIY additives don't work because I have zero evidence to back my opinion. On the other hand there is only anecdotal evidence that for instance  Ivermectin works. Anecdotal Evidence is a contradiction in terms and we really need a well designed study but as you point out if its a prohibited additive its not going to happen.

[John B 119]

You don't get empirical evidence unless people discuss it . And eventually after people have tried it and talked about it someone starts a study and lo, it becomes science.

[Psyche 941]

Ivermectin is/was all the rage in the BOI, but the latest is that it no longer works. IDK? 

I spoke to a paint tech a while ago and he said its application, location and season dependent, what organisms the marine environment is supportive of, temperature, end use and so on. That's why some people swear by Altex No5 and others have a very average experience. If someone uses it in a marina with low water movement and it works, that does not necessarily apply to a tidal location with lots of freshwater runoff.  Too many variables to promote or condemn paints by what's written on the tin, the best advice I got was use what works for everyone else in your area/use profile.

[motorb 58]

On 18/04/2026 at 5:41 PM, Quattro said:

I wonder if making copper fines and mixing in with AF would make any difference.   

 

On 19/04/2026 at 6:41 AM, Psyche said:

Pretty sure if it was that easy the paint companies would be all over it. 

Have you seen what copper costs these days? You bet they are using exactly as little as possible to compete in the market.

The reality is that the "good" stuff is all eventually banned, as by being toxic enough to deter growth it's also going to be problematic when concentrated in a marina "environment" (and probably not great for the humans applying/maintaining it either.)

 

 

I suspect the way forward from here is indeed homebrew mixes based on nothing more than old wives tales and anecdotes, or some ultra expensive engineered coating like copper coat.

[Black Panther 1,829]

I've had coppercoat 10years. I've saved more than enough 8n haulout fees to offset the cost.

[CarpeDiem 575]

For us it's been about regular maintainance and how much the boat moves. 

We had Ultra 2 for 6 years in Westhaven cleaned with a rag every 3-4 weeks. 

We redid it last September. Not because we needed to but because the boat had to come out for a week to drop the rudder.  I reckon it had another year left in it. 

I put Ultra2 Grey on again. 

In 5 years time I will look at Coppercoat again.  It's a bit of a major exercise... But it would be nice to get 12years instead of 6.

 

[Psyche 941]

The only issue with coppercoat for a race boat is getting a good finish.

[K4309 457]

3 hours ago, Psyche said:

The only issue with coppercoat for a race boat is getting a good finish.

I've applied CC to my boat twice now. Never had any issues with getting a good enough finish. That is unless you're the type of guy that likes to polish the entire hull with 300 grit wet and dry sandpaper. For us, the CC finish has been the same as any conventional AF we've applied. That said, there is no issue with sanding it either, so if you wanted you could sand it baby-bum smooth. I really doubt that makes any difference to boat speed though. My view using 300grit on your hull is more of a psychological effect, either for you, or a psy-op for your competition.

I have heard of poor applications of CC, randomly those are all connected to professional applicators. Black Panther being the most salient example. I think the professional applicators are always under time pressure with their schedule, and boat owners paying moonbeams for commercial hard stand, where as DIY applicators have far more flexibility to make sure the weather / climatic conditions are ideal for application. Warm enough, and low humidity so the hull, and especially the lead parts of the keel are warm enough and thus properly dry. I believe that is what influences the surface finish quality (warmth and thus viscosity of the resin component), moisture on the surface affects adhesion longer term.

Currently we are getting acceptable performance from CC regards biofouling, but we are getting nuked by barnacles (Weiti). But for context, guys who wash at the same frequency as us and use Altex #5 I think (a common, popular ablative AF, possibly Warpaint) are getting nuked exactly the same as we are. It's those damn northern boats bringing down the carnivorous barnacles from Opua 🙃

Other than the massive savings in haul out costs, the major benefit of CC is that it is hard, and you can clean it as often as you like. Obviously that benefit applies to other hard AF's as well. But CC is hard and durable for regular cleaning. We use steel scrapers to get the barnacles off and there is no detriment to the actual foul-coating. Being able to clean frequently can be a benefit for racing obviously as well. I think having a freshly clean hull is on the whole more beneficial than one that's had 300grit gone over it. That is all in relation to people using the popular ablative or semi ablative (partially soft) AF's. Very easy to wash off valuable quantities of AF by cleaning it, so people don't clean it as often or as hard.

So basically, in the absence of 100% effective AF's the next best option is mechanical cleaning, as opposed to chemical toxicity. It's like cleaning your roasting dish at home. You can use harsh chemicals, or just scrub the feck out of it with some good old fashioned elbow grease. They both get the roasting dish clean. And if chemical cleaners aren't available, you are only left with the mechanical cleaning option. But for that to work on a boat, you need a hard and durable coating.

Edit: What I would say for a race boat with CC though, is that CC tends to get a light fouling relatively quickly, but then doesn't really change over the next 6 months or so. That is fine for cruising, but if you want a perfect hull with CC, you are probably going to need to clean very frequently, probably every 2-4 weeks. The question then becomes, is there a conventional AF that works better? I'm not aware of one.

[motorb 58]

These Weiti barnacles are insane! Seems to be a lot of spawn in the water there and up around Kawau.

We never had anything like this level of fouling at westhaven, but thats different water in a different location ( and maybe all the road runoff plus 40 odd years of old school antifoul contamination has something to do with it...)

Oddly enough, closing the second entrance actually helped reduce fouling for us while we were there. Maybe it's the silt passing through on the tides that feeds the barnacles?