Nope.. other than the initial "jump the new guy" thing that happens with all new arrivals. Never had a disease/parasite problem. Then again, I have been going to LFS for years and I can tell most of the time just by looking at their tanks/fish if I am going to buy from them. I keep my water conditions pristine so none of my fish seem to ever be stressed out. I also never dump the water from the LFS into my tank. I always put a net over a container and pour the fish into the net, then release it into my tank. I do "float" the fish for about an hour and drip acclimate them with my tank water into the bag. Not the best practice and not recommended, but for me it has worked and I have been lucky.