The six line is a mellow little thing, never showed any aggression since I have had it. But I have only had these fish for a couple weeks. I only had the ten and five before and I didn't keep any fish in my five. Just corals and anemones, and that tank is only a couple months old at the most, but I used cycled liverock it was running good from day one. The ten gallon is great. I have it a little overstocked but there is a lot of hiding spots and there isn't any aggression, plus I was planning on an upgrade even though I will still be keeping the 10 and 5, if the fish need more room, the room is available. I have to keep the tank a little overstocked to keep enough algae for the lawnmower, but I love the little guy. I really like the smaller aggressives. I really wanted the orange banded stingfish but am affraid the mouth is just a little to big for the livestock I want to keep in the 90. Maybe someday I will convert my 29 gallon freshwater planted tank into a saltwater for one of those. Is the one you have different than the orange banded stingfish? Cause it looks more colorful.