Here is something to think about for people who think that fishy-thing works.
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Hobbiest has 150 liters tank, hobbiest puts couple fishes into that tank. Ammonia level increases, after that nitrite level. After that nitrate starts to increase. (Fishes suffered from ammonia/nitrite.)
Then happy hobbiest thinks that "Hey, my tank is cycled. Im going to buy more fishes" This happy hobbiest come home with plenty of fishes. Hobbiest puts those fishes into that tank, which hobbiest thought to be cycled.
Then happy hobbiest feed fishes and realizes something is wrong. Because hobbiest has some tests, hobbiest does those tests. Then happy hobbiest notices that there is some nitrite and thinks "What's wrong!? I cycled it with couple fishes already..."
**
So what was wrong?