hi, 
i got a flowerhorn 10 days ago, in the beginning he was all scared and would hide behind the rock.. but after he got used to the place he came around and now is all active.. his appetite is good.. he had stress marks when i first got him so his body was a bit black.. but that went away as soon as he got adjusted.. but a few days back he got black strips again but they dint go away.. i did a partial water change 2 days ago.. dint use any conditioner just made the temperature equal to his tank temperature and added it.. after that day his tail seems to have gone transparent.. if i look at him from far it almost looks like he has no fins or tail.. the fin is semi-black and transparent and so is the tail.. he is still active.. chases my finger and eats properly..i checked to see if it was fin rot.. but i really dont know.. this is my first fish and i dont want anything to happen to him.. could you please help me out and tell me what is actually happening..