if ich kills 2 fish and 1 fish survives and recovers and builds up an immunity...

[peasofme]

if ich kills 2 fish and 1 fish survives and recovers and builds up an immunity to the ich, when would it be safe to add another fish?

[leebca]

Ornamental marine fishes in captivity don't really build an immunity to Marine Ich -- not like they do in the wild. First off, fish immunity is nothing like animal/human immunity. It is a scaled down version of human immunity, yet it is better immunity than say invertebrates.

In captivity, the infected fish keeps fighting the disease, is under constant stress from the fighting, and is like a bomb waiting to explode. Given additional stressors like bad water, not being http://www.reefland.com/forum/marine...nutrition.html, another fish, environment, introduction of another fish, etc. and the Marine Ich will 'come out' in full force.

I wish you had a microscope and know how to take samples from your fish. Because if you did, you'd find the fish was still infected and the tank has Marine Ich in it.

What you are not seeing is the single point/stage (in the parasite's life-cycle) where the parasite becomes visible to the human eye. This can be happening at night (the MI parasite likes the dark) or in the gills. It can be a single spot that you don't see or ignore. But, the fish is in fact infected and the tank is also. The parasite is just waiting for more hosts or for the host it has to become weakened to bloom again in large numbers -- which then you will see.

It is not in the parasite's best interest to kill its host, but in captivity our stressed fishes in a small space like the tank, do die fairly quickly.

[mk1151]

Without knowing what else you have in your tank, another option is a few neon gobys. I had one fish in my tank with what might have been Ich and it was suggested I add them to get rid of it. As soon as I put them in the tank, my fish in question went straight to them and just hung out while they voraciously cleaned it. Within a day, I could see no visible "maybe ich" left, and all the other fish in the tank, including a large trigger that could technically eat the goby, "asked" to be cleaned.

In a reef tank with LOTS of LR, you can't always get a sick fish out of the tank, so cleaners, Ich-eaters, and a UV filter/pump are your friend.

I also highly recommend, as Leebca has said a number of times, use a QT with new fish. You'll never catch everything but you can get the big stuff.