African Brown knives can reach a foot. They usually don't in aquariums because of tanks like yours where they are crammed and slammed and prevented from growing.
I like how you still refuse to admit how high your nitrates are.
My nitrates are great. 5 to 15 ppm without serious planting is outstanding. My tap has 0 nitrates, so it all comes from the tank's inhabitants.
The reason nobody wanted to respond to your post should be even more evident to you now. You have your fingers in your ears and you're screaming, "La, la la!". How is reason supposed to reach you?
I fail to see how I've been rude to you. You ask the question, I tell you the truth, you cry about it. If you don't want the truth, don't ask for it.