That is a very real concern, however, My fish, corals, rocks, sand and every drop of water all come from one location that I dive/snorkel on twice a week and have never seen a holding tank or anyone elses tank for that matter. Everything goes from the ocean to my tank in a matter of an hour or two. When I do return fish or corals, they go back to the same exact spot I got them from. Never had a disease either, fish or coral. I also just returned an elegance coral since it grew far too large for my tank, was taking over the entire left side. It is out on the reef to where I will see it each time I head out so that I can check on it as I pass by.I admire your action. and agree a sailfin tang is way to large for a 55.
but it brings into question some concers as well.
captive fish being release back into the wild.
I was always under the impression that is a bad idea. pathogens etc that captive fish may be exposed to.
not to try and be off topic but I wonder how others feel about it.
My Reef Tour