Your argument against baby fish in the water makes no sense. A little bit of natural soap or soap containing salt wont harm the fish. For a start, there's already small amounts of salt in freshwater or lakes, aswell as other minerals. People, other animals, boats, and all-sorts of dirt go in that water. Joey mentioned the sweat from people washing in it, i mentioned animals excrement, and other natural pollutants that happens daily.
It wouldn't be called sailor soap or soleseife soap if a normal soap with a high coconut oil content worked exactly the same, which makes the soap made with salt water more versatile than a standard bar. And since its different to a salt soap bar, it shouldn't be any harder for a beginner to make. Wither you use plain water, brine or beer, anyone can make it, although i do agree that a salt soap bar (adding salt to the batter) could be harder to make for a beginner. And even that is more versatile because it acts as an exfoliant.
I'm wondering how to came to this conclusion; aka if you have education/training that can help us understand this better, please share. It would be very helpful for soap makers to know in the future.
But I'm concerned you're coming from a standpoint of assumption; aka "Nah, I'm just one person washing in one stream this one day, so I'm not going to hurt anything."
Water is a miracle. Please people. Don't assume that because you're one person with one bar of soap/detergent, washing 2 plates and a cup, that you don't have an affect. These guidelines exist worldwide for a reason.
Water is a polar molecule with a very special electrical charge, and that polarity is what makes water miraculous. It's why a drop of water on the counter mounds up (surface tension), it's why ice floats despite having the same density as water. Soaps and detergents break that electrical bond, therefore changing how water behaves. It's why the tiniest vessels in your capillaries can still carry blood. (capillaries can be so small that only one red blood cell can travel through at a time!)
I've kept freshwater aquarium for 20 years. First rule of fish keeping is never let anything that was EVER been washed in soap near your fish. Why? Because it never completely washes off. You can take an old used aquarium out of the attic, scrub it out with soap and rinse 100 times with vinegar and water and still have residue that will affect the health of your fish's ecosystem. Might kill your fish in days. Might not. But it will degrade the protective slime coat on your fish t hat is an important part of it's immune system, and 3 months later you'll be back at the fish store.
And salt, or soap on frog eggs, fish eggs? Tadpoles? Algae and water plants? Let's think about this:
I live near at the ocean where my local nursery has a list of veggies and plants that won't survive if your garden is with so many yards of the sea - because the salty moisture in the air will harm/kill them. People use salt water to kill weeds; plant their petunias in the same place and then wonder why they won't grow. Soap is used an insecticide.
Does one person washing 2 plates and a cup in a stream make a difference? Yes. Not the least of which is because that stream is part of a very long water system that with more streams, rivers, ponds, lakes, oceans. There are other people hiking along that stream, washing their dishes, hands, or clothes. The soap you use can break the polarity of the water, and starve water life of oxygen.
For anyone interesting, a short article with basic explanation on water's polarity and why it makes life possible.
Properties of Water & Water Polarity Science Lesson | HST
But I think this simple kid's experiment might help people visualize the power of polarity:
