FWIW, I currently have a three month old system and use a QT (10G). I have done my research and reading and my personal opinion is that it is better to be safe than sorry as far as dips go. That said, it seem to be common practice for large aquariums to dip their livestock before adding to a display tank. This is a practice I have followed since I started adding my livestock. I use methylene blue (stains like the devil though)
, which is an oxidising agent which actually helps getting oxygen the the fish. I have a set of tools and buckets that I have and use only for the QT. I make up about 1 - 1 1/2 Gallons of
RO water, which I bring up to temperature. For this I use a small submersible heater and in addition I add an airstone to keep circulation going. I also float a small glass thermometer just to make sure that I am staying to temp. After acclimating the fish, I pour it into a breeding container. This has slots so that the water runs out and I can move the fish without a net and without the shipping water. The fish is then immersed in the freshwater mix for about 2 minutes. I manually move the container up and down to keep circulation brisk. After that, I drain out the water and transfer the fish to the QT. So far in my display tank I have 4 yellow tailed damsels, and a Naso Literatus that have all gone through this procedure. This past weekend I just added 3 Banggai and a Royal Gramma to the QT.
Methylene is the gentlest medication to use for this as it is harmless to smooth skin fish as well. Just be aware that once you make up the dip, you cannot see through it, as it is a very deep blue. That is another reason to use a container to immerse in the dip.
Anyway to make a long story short, I have used it successfully so far and I plan to continue to do so. I figure that anything I can do to lessen the chance of introducing some pathogen into my display tank is a step worth taking.
HTH 8)