ich on only one fish

[ehh]

i dont have this issue but im curious.
ive seen it in a tank where a couple fish will have ich and the rest will be totally fine.
i always thought this was because the surrounding fish had strong immune systems and could fight it off. but is that the truth for ich?
someone recently told me its species specific but that makes no sense to me as its a parasite and i would think the offspring of the parasite is just looking for anything to latch on to.

???

 

[duanes]

I recently had an infestation of ich spread thru one line of my tanks, the line has 6 tanks, all plumbed onto the same sump, and has a distribution of about 8 different species.
6 species became infected, 2 showed no sign at all.
The unaffected species were both in the tanks with the highest flow/turnover rates.
Maybe the high flow made it harder for the planktonic stage to take hold, and maybe I started the treatment in time to catch weaken the planktonic stage is fast flowing water.

 

[convict360]

I've also found this, that new fish that get ich can get it very quickly; but existing fish show no adverse affects. I'd be guessing immune system personally, but if left untreated I guess all fish would get it eventually in the same system

Sent from my Nexus 5 using MonsterAquariaNetwork App

 

[lardieleftover]

Well some fish are more likely to get ich when moving/ or scaleless. The high flow you had in those 2/6 tanks probbly did keep the ich from attaching, or that those fish were stronger from fighting higher current.
Interesting problem still.