I dont have a nano either but I do have both in my 120. The blue legs seem to eat more algae and be a little more aggressive towards the scarlets. My scarlets are very cool looking but seem to be the lazier of the two!
Kyle
I HAVE BOTH IN ALL THREE OF OUR TANK'S I THINK THE BLUE LEGS EAT MORE ALG. BUT I HAVE SEEN THEM KILL SNAILS TO TAKE THEIR SHELLS WHEN THERE ARE SHELLS LAYING ALL OVER DANE