I had some Diamond Tetras in a 10 gal once and would have to say no. These are very active fish and fast. They like to have lots of room. In my 10 gal they were very active at first until about 2 months later they would just stay in one spot and looked bad. Moved them into my 55gal and within 15mins they were active and showing good colors. I would say 30gals or more for Diamond Tetras.