I always have a good number of neons and/or cardinals in my tank and I've had both fairly equally mixed in schools of 15-30 at various times. If you know what you are looking for, then you can see the difference and it is a matter of personal taste as to whether it looks good or not. I was fine with it. About a year ago, due to a UV incident, I wiped out my school. I replaced the school with neons only, despite the fact that cardinals are hardier. I had grown tired of the intense color saturation of the red and blue in the cardinals. At some point, I may start adding them again if I find I miss that effect and, if I do, won't hesitate to mix them with the neons again.