Why do new fish get Ich when you add them in your tank?

homersimpsonlikesfish · Jan 1, 2024

Why do new fish get Ich when you add them in your tank? And how does this happen if they don't have Ich at the fish store? Where exactly is this Ich coming from?

ISpeakForTheSeas · Jan 1, 2024

homersimpsonlikesfish said:
Why do new fish get Ich when you add them in your tank? And how does this happen if they don't have Ich at the fish store? Where exactly is this Ich coming from?

To my knowledge, the answer is that they do have ich at the fish store, but - with either ich management techniques used in the hobby, copper medication/hyposalinity in fish store tanks (from what I've heard, in most cases it's probably this one; non-therapeutic levels of copper/hypo), or a combination of the two - the ich is suppressed (not eliminated) at the store.

So, when you bring the fish home and it gets stressed by travel and the new environment (and doesn't have copper or hyposalinity suppressing the ich), it's immune system weakens from the stress, and the ich pops up seemingly from nowhere.

EeyoreIsMySpiritAnimal · Jan 1, 2024

+1 on fish stores "treating" fish with sub-therapeutic levels to mask any ich...

Lavey29 · Jan 1, 2024

I agree with the above, hence why I believe ich exists in every tank and we all just keep it at bay via ich management with proper non stress environment for our fish.

Spare time · Jan 1, 2024

I think it's because they were in water with the ich or ich "eggs" and some of that got carried over. I don't really buy the idea of subtheraputic levels of copper masking ich as the fish either has an infection or it doesn't.

EeyoreIsMySpiritAnimal · Jan 1, 2024

Spare time said:
I think it's because they were in water with the ich or ich "eggs" and some of that got carried over. I don't really buy the idea of subtheraputic levels of copper masking ich as the fish either has an infection or it doesn't.

There's nothing to "buy"...

F i s h y · Jan 1, 2024

EeyoreIsMySpiritAnimal said:
There's nothing to "buy"...

Agree. Specifically hyposalinty masks ich. Your fish store is likely running salinity at a lower level than your reef. 1.021 versus 1.025 or 1.026... this causes the ich to lay dormant until it finds a suitable environment.