I have 14 male guppies in a 60 litre tank with a substrate of Caribsea, live plants, bog wood, water quality all tested and normal, temperature correct. I also have a couple of very small cherry shrimp and one small very placid golden nugget pleco. I water change roughly once a week and have had no problems. I have had the set up for approx 3 months. I feed a mixure of blood worms, daphnia, Tropical flake food, Novo tabs, alage wafer (not all at once! just to give a variation) once or twice a day. Today I have noticed 4 of my guppies have great chunks out of their tails Is this a dominace thing? Can I prevent it? Any suggestions gratefully received