"Cycled" and old tank always at 0.25 ppm ammonia

[NewShrimp]

Hi everyone!

For the past 3 months, I have been cycling a 3 gallon tank for my shrimp. I rinsed out the tank thoroughly before adding substrate, calcium carbonate pebbles, lava rocks, macroalgae, and the supershrimp moss ball, all of which I bought from the store here. I used distilled water and the salt from the shop to fill up the tank. There is no sign of green algae, but it seems like some sort of algae is beginning to grow on the sides. The 3 gallon tank has a light, but I have it in a well-lit room where it receives lots of indirect light and some direct light in the morning, so I don't use it. I was hoping to move my shrimp over from their tank this week to the new 3 gallon tank. I tested the water parameters in the new 3 gallon tank with the API Freshwater Master test kit. I got a reading of 0 nitrate, 0 nitrite, and 0.25 ppm ammonia. I'm starting to question if there is actually any ammonia in the tank, or if it's just difficult to read the API test kit results, as I am always getting a result of 0.25 ppm ammonia in my current shrimp tank. My API test kit is not past the expiration date, and I always thoroughly shake the bottles and closely follow the directions when testing the water. My current 1 gallon tank with 2 shrimps was set up similarly to the 3 gallon tank. It was cycled for 4 months, and it has substrate, calcium carbonate pebbles, and macroalgae from the store. I added in a little rock-shaped house for them that I bought from a pet store. It is aquarium safe and I rinsed it thoroughly before adding it. The 1 gallon tank was filled up using distilled water and salt from the shop. I had a problem a few months back in the 1 gallon tank where one of my shrimp seemed extremely sick. When he was sick, the API test kit reading said 0 nitrite, 0 nitrates, and 0.25 ppm ammonia. I was doing 25% water changes every other day, and was then advised to do a 90% water change. Even with all of these water changes, the tank still continuously read 0.25 ppm ammonia. I gave up changing the water, as my shrimp ultimately recovered, and they are both fine and active to this day, even though to this day it still says there's 0.25 ppm ammonia in their 1 gallon tank. Their current 1 gallon tank is about a year and a half old, and is in the same area as the cycling 3 gallon tank, where it receives lots of indirect light and some direct sunlight in the morning for about an hour. I have only ever fed the shrimp in their 1 gallon tank once, which was when they were first added to their 1 gallon tank (they came from an ecosphere). I fed them a pellet, and I removed the remains of it after a few hours. I have not fed them since because I'm afraid of overfeeding, and there are only 2 of them. Their bellies are always visibly full from finding algae or bacteria to eat in the tank. There has never been any food added to the 3 gallon tank yet. With all of this said, I have absolutely no idea why I'm getting an ammonia reading in both the current 1 gallon tank and the cycling 3 gallon tank. If there is truly ammonia in the tank, I have no idea what's causing it. There's no rotting food or any other matter in either tank, and I'm at a loss at this point. Is it possible that both the 1 gallon and 3 gallon tank aren't cycled?

I have attached 2 photos showing the ammonia test result from the 3 gallon tank. The one photo shows the result in a well-lit area and looks cloudy and like it matches the 0.25 result, while the other photo was taken in the same area with my phone's flash on, and it looks like it matches the yellow 0 ppm result a bit more. I have also attached photos of the "cycling" 3 gallon tank, and a photo of the 1 gallon tank. It's difficult to see the algae growing on the sides in the 3 gallon tank, but something is definitely growing on the sides (looks like smudges, almost like fingerprints). I also wanted to note that the macroalgae in the 1 gallon tank was once a deep green, but it slowly became more pale in color. Not sure why that is, or if it's rotting. Even when it was a fresh deep green, the ammonia reading was still always 0.25 ppm. Is the macroalgae rotting in the 1 gallon, and if so, what causes it to rot? There is shrimp poop all over the macroalgae, as that's one of their favorite spots to be, but I'd assume that their poop is only beneficial to it?

Thanks for all the help!

[Fishkeeper]

Since you never got an answer:
This is because the API test kit usually displays 0.25ppm ammonia. You don't actually have ammonia.