We've had a red coral goby doing well in our tank for awhile now and just got a green one. I ensured the dealer would take it back if there were territory issues as it's not a massive tank - about 20 gallon display and I had concerns. Actually they are very peaceful and always together. Would this indicate they've become a mated pair? The red one has developed a more elongated body quite quickly and is far more confident and out and about since the other went in.