I dont but i will soon , not so much for desease but more so to make sure the fish is eating well .

I've got a pretty simple 20gal with heater, T5 fixture, and two koralia power heads. I rarely ever buy fish these days and the ones I do acquire tend to come from friends so I don't bother with them. But I do quarantine all new coral and clams. Quarantining has saved me from re-introducing red bugs, majanos and perhaps a few other pests on a couple of occasions.

My main system is 240gal.