It could have been that the cories were the vector, or that ich was already in the tank, and the chnages of adding new fish were enough to bring it to light. As a general rule (very general) if the new fish were the first to show signs, then ich was already in the tank. If the fish that you already had were the first to show signs, the ich probably came in with the new fish. Immune response with fish (still lacks a lot of science) usually shows that fish which are already exposed to active ich will not break out as severly as non-infected fish that become exposed to it. In other words if the cories had a subclinical infection and brought in ich to a tank that did not have it. then the fish in that were already in that tank are most likely to manifest a severe outbreak. By the same token if the fish in your tank had a sub-clinical infection, and the cories were did not then the cories would manifest an outbreak first.
And of course it's always possible that the cories and your existing fish both had ich, and the slight stress of adding new fish allowed it to show u in a very minor outbreak.
Ich will attack the gills of any fish healthy or not. The slime coat of the fish will often stop visible signs of ich externally, but the gills do not have a slime coat and will remain vulnerable at all times.
As Bill pointed out ich multiplication is massive. When ich hatches it has to find a host within a few hours or it dies. In the wild, the odds are very much against ich. Large water volumes, few fish and a lot of movement of host from area to area. The survival mechanism of this fish is its reproductive rate. each ich cyst you see on a fish will produce several hundre to a couple of thousand freeswimmers. in the wild only one or two of these may ever find a host. in our tank they almost certainly will.
Gravel vacs and water changes definately help with removal of large numbers of parasites.
I personally would not ever reccomend that anyone try to let the fish's natural defenses fight off ich. Ich will survive hidden in a tank only to show up again in a bad way when something else stresses the fish.
Although heat alone will kill ich, I do not trust it as a treatment method because it is hard to govern heat precisely in our whole system, and one cool spot could feasably allow ich to survive. Heat does speed up the life cycle and get the ich off of your fish sooner, and if ich is exposed to temperatures above 86*f As I understand it it will prevent reproduction and kill off any hatching freeswimmers. Any elevation in temp will help the cause ifsomething is in the tank to kill ich when it hatches. If there is nothing in the tank to kill ich then raising temps will only bombard your fish with even more parasites to try to fight off.
The sensativity to salt that many fish are said to have is relative to the purpose of your situation. Pleco's cories angels etc do not like salt particularly. It increases dissolved solids levels and makes the fish uncomfortable.
Salt will also form a "layer" near the bottom of the tank if not mixed well enough, and fish such as cories that live primarily on the bottom will be exposed to heavy brine levels. With properly mixed salt you should be able to treat at the needed levels for the needed time period without issue.
Salt, meds, ich, and high temperatures all create a degree of stress. of the four, higher temps and salt will most likely be the least stressful and most beneficial. I have treated many pleco's with salt at and above 2 teaspoons per gallon and have not had any give in to the effects. There are signs of stress at times, and one should proceede very carefully and slowly but I'd rather put my pleco's through two weeks of uncomfortable salt levels than years of ich on their gills. The article linked above has a lot of detail, and I sincerely hope it's worth the time to read (If it's not I failed in my purpose)
HTH
Dave
And of course it's always possible that the cories and your existing fish both had ich, and the slight stress of adding new fish allowed it to show u in a very minor outbreak.
Ich will attack the gills of any fish healthy or not. The slime coat of the fish will often stop visible signs of ich externally, but the gills do not have a slime coat and will remain vulnerable at all times.
As Bill pointed out ich multiplication is massive. When ich hatches it has to find a host within a few hours or it dies. In the wild, the odds are very much against ich. Large water volumes, few fish and a lot of movement of host from area to area. The survival mechanism of this fish is its reproductive rate. each ich cyst you see on a fish will produce several hundre to a couple of thousand freeswimmers. in the wild only one or two of these may ever find a host. in our tank they almost certainly will.
Gravel vacs and water changes definately help with removal of large numbers of parasites.
I personally would not ever reccomend that anyone try to let the fish's natural defenses fight off ich. Ich will survive hidden in a tank only to show up again in a bad way when something else stresses the fish.
Although heat alone will kill ich, I do not trust it as a treatment method because it is hard to govern heat precisely in our whole system, and one cool spot could feasably allow ich to survive. Heat does speed up the life cycle and get the ich off of your fish sooner, and if ich is exposed to temperatures above 86*f As I understand it it will prevent reproduction and kill off any hatching freeswimmers. Any elevation in temp will help the cause ifsomething is in the tank to kill ich when it hatches. If there is nothing in the tank to kill ich then raising temps will only bombard your fish with even more parasites to try to fight off.
The sensativity to salt that many fish are said to have is relative to the purpose of your situation. Pleco's cories angels etc do not like salt particularly. It increases dissolved solids levels and makes the fish uncomfortable.
Salt will also form a "layer" near the bottom of the tank if not mixed well enough, and fish such as cories that live primarily on the bottom will be exposed to heavy brine levels. With properly mixed salt you should be able to treat at the needed levels for the needed time period without issue.
Salt, meds, ich, and high temperatures all create a degree of stress. of the four, higher temps and salt will most likely be the least stressful and most beneficial. I have treated many pleco's with salt at and above 2 teaspoons per gallon and have not had any give in to the effects. There are signs of stress at times, and one should proceede very carefully and slowly but I'd rather put my pleco's through two weeks of uncomfortable salt levels than years of ich on their gills. The article linked above has a lot of detail, and I sincerely hope it's worth the time to read (If it's not I failed in my purpose)
HTH
Dave
