hi i have a 55 gal. i put a briareus in the fully cycled tank. he was doing great for about 1 month and stoped eating. then he started to breath very heavy and died 3 weeks later.last month i got a macropus. he ate like a pig and looked very healthy. last night i put food in his tank and he would not eat first time ever. this morning he was on the glass breathing heavy just like the briarius.all water test are fine. nitrate was high 2 weeks ago but they are about 20 ppm now. i bought the tank used. i rinsed it out very good when i bought it. is it possible there is traces of copper in the tank even though i rinsed it out? i just checked on him and he moved to a different spot but still on the glass w/bad cork screwed arms. i put alot of carbon in 10 mins. ago. does anyone know why i lost 2 octos. is it the tank? i have a diff. 55 gal. w/a bimac. i have had him for over a year. and as far as the one that lookes like he is not going to make it i did get as much info. i could on him . he is a baby macropus.any help please. thankyou jimmy.