Hi I'm new to this site I've been cruising around it for a while and its answered alot of my questions but I need some advice for starters me and my fiance have two tanks we have a 55 gallon and a ten gallon we inherited the 55g tank from my mom and she had 6 huge goldfish in it and 4 danios. Us being new to tank owning we bought a dragon fish or a violet gobie I don't the proper term for it but it was the firstfish we bought and the idiots at PETCO said it would be fine with the gold fish well after going to our LFS we realized. We had to get the goldfish out of there so we got rid of them and kept the danios stripped the tank and started fresh we were feeding the dragon fish frozen blood worms on a daily basis well the dragon fish got mouth rot and I'm not sure if it was the bloodworms or the goldfish but we stopped feeding him the frozen blood worms and treated him and he seems to be doing better but sadly it got pretty bad before we noticed because he's very evasive and its really bad and I'm not sure what to do we're. Doing the water changes regularly and keeping it at a good tempature but I feel like he's suffering at it just makes me sad is there anything else we could do to save him? All suggestions are welcome I just feel so bad for the little Guy