I have to be the devil's advocate here ..
Anything you add to your tank can
potentially add bad things to your system
I don't QT shrimps, snails, hermits, corals, etc, but any one of these little guys' shells/skeletons can harbour
bad things
For example;
If Marine Ich likes to attach itself to substrates, aquarium parts, LR etc, why would it not also attach itself to, for example, snail and hermit crab shells ?
I haven't QTd everything I've ever introduced to my DT, but I'm rolling the dice, or rather, spinning the cylinder, so to say
I like what Anthony Calfo said ...
"Not using a quarantine tank is like playing Russian roulette. Nobody wins the game, some people just get to play longer than others." - Anthony Calfo