Oh, in that case, what tetras do you have?There's a couple tetras in at the moment. I probably didn't describe well enough, sorry. The tank has been running for 11 years now, just not kept up with as it should've been and there hasn't been a decent amount of fish for a while. I am aware of the nitrogen cycle to answer your question.
Welcome to FishLore, Joedusa.4 !!