Except for 1 occasion, I've always QTd fish into this tank. This is mainly to prevent ich and Almyoodinium. I try for a 4-week QT. For grazing fish that may be difficult to get to take prepared foods like a mandarin, QT has been as short as 2 weeks. I try to set up the tank to give such fish enough graze, but its a small volume, so typically the graze runs out. I have encountered one external parasite during a QT period, which only became evident because the fish was QTd (visible egg case developed). I believe I have also encountered Almyoodiunium on a new fish in QT. Strangely, I've never encountered ich. Anyway, in my limited experience, using a QT for fish is a good idea.
I brought all my clams in as a batch order and did a 7-day QT. These later had to be dipped for the pinching condition that didn't start to show up until about 2 weeks after I got them. One of the clams took the treatment (FW dip) very hard and was kept isolated in a QT for over a month until it looked fully recovered. FWIW this clam survived on DTs (or its own energy reserves) and PC lighting for that entire period.
Other invertebrates and plants have gone directly into the system. The only pest I've picked up off of either, to the best of my knowledge, was a sundial snail, which was easy enough to find and remove. A shipment of live sand brought aiptasia into my system. Some rock from a tank being torn down brought in red flatworms. Neither has become a plague, but I wish I had taken measures to prevent them.
