6 SAEs in a 40? Be careful. They grow up to 5-6" in six months or so and love to swim fast and play tag. Might hit the glass hard, mine do and I have a 75 long. They are known to accidentally jump out but mine haven't (my mollies do though). I have occasionally seen them with bruised noses. I have/had 4 until my DO2 dropped after a water change and I forgot to plug back in the airstone. They are first fish to die in low DO2 conditions. My discus, cories and loaches all made it.