Antibiotics, as in human medicine, is not the panacea. In fact as Harro has
pointed out they pose some risk to people who use them without care or
understanding. If youcan get an accurate ID on the bug then it helps a lot
as far as long-term management goes but not the individual fish are
concerned.
Rod Pick noticed a rise in Temp as a trigger, others claim the opposite.
The bottom line is "stress" in the broader sense. For each species there is
an optimum temp range and extensions either way could be stressful. It
appears that the immune system of the fish often has the TB/UD on hold
until the stressor factor operates and then out come the ulcer.
Remember that other hidden manifastations are probably going on
microscopically in internal organs even though there are no overt ulcers
present.
Lighting has been well studied by the Aquatic plant folks and I recommend
the List comparable to this one to anyone interested. Plants do best with a
continuous period of lighting. Animals of various types have been subjected
to a plethora of lighting intervals - usually for the purpose of intensive
raising for human food. From memory major increases in growth have been
recorded but in my opinion if the welfare of the animals and the long-term
health and longevity is important to us then we should go back to nature
(as we do with the plants) and offer them a 12/12 cycle or thereabouts.
Bruce Hansen