I have had up to 12 cleaner shrimp in a 75g.
It took over two years to deplete to only 1....
The shrimp will offer no real help for ich IMO.
I DON'T GO for let it go or it will be ok when it comes to ich.
Not even a little!
I lost a tank full of fish($$$) when I added a cheveron to my powder blue in a 120(4 foot /my fault)...
Only 3 'sure fire ' ways to eliminate ich ,not neglect it into hiding,which may be why some think it is in all tanks?....
If you didn't use one of these methods or allow total die off of your fish and leave tank fallow for months then you probably DO have ich in your tank IMO.
Copper
Hyposalinity
Transfer method.
Good read for those with ich....
Marine Ich - Myths and Facts | Reef Sanctuary
Most healthy fish may be able to fight it off but part of a tangs defense is to swim up to 25miles daily to get away...
That ain't happening in ANY of our tanks...
IMO tangs in under 6' long tanks are a risk...
More then 1 is doubling the odds against you and the fish...
Just figured one person who is willing to say you are in trouble with the ich if you don't treat it might be an honest refreshing approach to marine ich.
I feel this post will end like most others regarding marine ich....
DEAD FISH!
I laugh at freshwater ich and cringe at the thought it could still be in my 120 reef!
I can't afford it!