I am new to the aquarium world, but my boyfriend has had one for several years, usually containing Angel Fish and Mollys. We recently reset up the 55 gallon tank. We purchased 4 Small Angels, 2 Mollys and 2 White Tip Sharks. We lost one of the sharks within 4 days. The other is my little fighter (I named him Nev "Catfish") He was upset for several days after the passing of his buddy, but I did what I could and researched this fish extensively. I've learned quite a bit! He seemed really good. Yesterday I noticed he had white spots all over his body, but was acting normal. I went to an experienced aquarium store here in Colorado. He advised me that it was Ich and to treat the water with Metronidazole. I learned before medical treatment you need to do a 25% water change, I applied the dechlorinator/water conditioner and let it sit to room temp. Now I had a freshly clean tank which made Nev very happy. I then applied the treatment and to my dismay I woke up this morning to find Nev at the bottom of the tank covered in MORE white spots and his belly appeared strangely discolored and is laying at the bottom of the tank. I am trying to attach the picture here using the forum, but it will not get past 26% (any tips). He is still alive but however I'm not sure for how long? Please tell me what I can do! I have become very attached to this fish and don't want to lose him. Did this metronidazole do this??? I am aware this fish is a Brackish water fish and will grow extremely large. I am willing to do whatever it takes to accommodate him. He is currently VERY small not even 2 inches in length. We did however purchase them from a local franchised petstore, which with my research seems to lead to a lot of sick home aquariums I will not make that mistake again. Thanks... and information is helpful!