We have 20 Blacktip Reef Sharks ( Carcharhinus melanopterus ) in 400 m3 tank. We have had them for over 1 year now but lately, I have noticed their chin getting fat and unusual. It looks like they have a tumor(i send you some of their pictures). Beside that, They are doing fine and eating nomal but i'm so worry. I dont know it's just they are too fat or it's a disease sign. I looked up everywhere but I cant find anything the same.I hope you can give me some advices. Here is condition of my tank: pH: 7.8, Ammonia: 0 mg/L, Nitrite: 0 mg/L, Nitrate: 0 mg/L, Salinity: 29 ppt, Temperature : 29 OC. its tankmates are 9 stingrays, 14 small turtles and 5 whitetip reef sharks (whitetip reef shark 's chin are nomal ) We feed the sharks with fish and feed them once in 2 days. please help me! Any advice from you guys would be appreciated. 
i dont know how to upload pic in this site so i give you the link online. http://nn8.upanh.com/b6.s28.d2/3edcb6f36c297e3739a9ddd99fc33357_45772428.dsc0007.jpg
http://nn2.upanh.com/b2.s26.d2/e09ebb700b41cd31ec08db0968d07238_45772432.dsc0008.jpg
http://nn0.upanh.com/b2.s28.d1/66c14460b61bad95d0e022daa0e84980_45772440.csc0016.jpg
i dont know how to upload pic in this site so i give you the link online. http://nn8.upanh.com/b6.s28.d2/3edcb6f36c297e3739a9ddd99fc33357_45772428.dsc0007.jpg
http://nn2.upanh.com/b2.s26.d2/e09ebb700b41cd31ec08db0968d07238_45772432.dsc0008.jpg
http://nn0.upanh.com/b2.s28.d1/66c14460b61bad95d0e022daa0e84980_45772440.csc0016.jpg
