That would be a grammatical error on my part. In the past I have used Penguin biowheel hang over the back filters. I just checked my email order confirmation, they are infact penguin tetras, sorry for the confusionHaha that's too funny. I do have a question though, from my understanding you said you had penguin tetras earlier in the thread but then you said you only have emperor tetras left? Did you get both? What happened to your penguins?