Pools without chlorine/sanitization?

I’m looking at putting a small 1,300-gallon pool on my deck. I can't use chlorine because my son has a medical condition that makes chlorinated water a huge no-go for him.

I’m wondering if salt is an option. I see people recommending about 3 kg of salt per cubic meter, but they also say you need an electrolysis system to make it work—and honestly, those systems are way too expensive for a little setup like this.

In your experience, how many days can saltwater at a 0.3% concentration sit before it goes bad? I don't want microorganisms blooming and making the water dangerous for swimming. The pool does have a filter pump to catch any debris.

Look, I know what you're going to say: "Just change the water every day." But doing that means draining 1,300 gallons * 30 days, which is basically 4,000 gallons of wasted water or $667 a massive spike in my monthly utility bill. I’d much rather find a way to make the water last maybe 7 days, even if I have to throw in extra salt to get there.

But can you even have deficiencies without chlorine?
I honestly think it might be worth checking with a local pharmacy or a pool supply shop; they might carry something suitable for a pool that doesn't rely on chlorine.
At first glance—though please keep in mind I’m just a layman here—potassium permanganate comes to mind. A small box should cost less than $3.25.
I know for a fact it's commonly used in the aquarium hobby.

I was just doing some research, and apparently, potassium permanganate is even used to disinfect drinking water, which means you could potentially use it in a pool. Just be incredibly careful with the dosage—only two or three granules for every 10 liters should turn the water a light pink color. It’s so easy to overdo it, isn't it?

rustymason82 said:I just did some digging, and apparently potassium permanganate is actually used to disinfect drinking water, so it could work for a pool. Just be careful with the dosage—maybe two or three granules for every 10 liters to get a light pink tint. It’s incredibly easy to overdo it...

Using potassium permanganate is an interesting thought, and definitely worth looking into. But we're talking about a kid here who is allergic to almost everything—even things most people don't even react to. Chlorine is also used to treat drinking water, just in tiny amounts. That’s why I was leaning toward salt as the safest bet, though the real question is how long the water will actually stay clean if we don't hook up an electrolysis system.

You can grab chlorine-free pool treatments, probably ozone-based, sitting right there on the chemical aisle at Bauhaus