Ich w no new fish added??

[Tro]

Hello,
A couple days ago I wrote a post about installing a new radion light in my fish tank. When I added the light my fish were clearly stressed out for several days following. About 3 or so days after adding the light my hippo blue tang started acting irritated like it had a parasite. Yesterday a small speck that looked like sand appeared on his nose. It looks like ich to me.
This is very strange to me because I have added nothing besides the light to my tank in well over a year. No live rock, live food, inverts, absolutely nothing live, or from another tank has been added to my tank in over a year! I'm so confused.
I've been doing some research and am wondering if ich can just pop up when fish are stressed? There seems to be mixed opinions on this topic. What are your thought? Any links to good reads on the subject?
Thank you!

 

[cougareyes]

In 30 years I have had many tanks. I have had ick twice, both times were in tanks where there had been nothing added for quite a while. In both incidents I can figure a stressor which sparked the onset of the disease. So the simple fact is there are some fish that are carriers and if their immune system becomes compromised and there's a stressful event, bam.

 

[scooter31707]

Ich was present in your tank, for how long was the question. Their immune system was fighting it off until as mentioned above, something stressed them and surprise. Best bet is to take out all fish and go fallow for at least 72 (90 even better). if you need some holding tanks Petco is having the $1/per gallon sale.