Is ich usually incidental to something else?

[jlindseyjr]

Came down with a case of ich. Two of the platies have spots. Everyone else looks ok. Increased salt to 1 tbsp per 5 gal and raised thermostat on heater to 86°. I'm trying to figure out if the fish are sick because of the ich, or if the ich is incidental to some other malady. The platies and cories were the first fish in the tank. A week later I introduced 3 of the mollies. A few days went by, and I realized I mis-sexed one of them, so I bought two more females this past weekend. A couple days ago, I noticed the male platy had taken to just sitting on the bottom, occasionally swimming around, but very skittish. This morning, I noticed white spots on him and one of the females. The others look ok. Could the platies have been that stressed by the introduction of the mollies? I don't see any symptoms of anything else.

Tank Stats
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Size of Tank (Gallons / Litres): 20 gal
Running for how long: 3 weeks

Water Params
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Temp: 76
pH: 7.2
Ammonia (ppm): 0
NitrIte (ppm): 0
NitrAte (ppm): ?
Water-change Schedule: weekly
Water-change Amount: 15%
Any Water Additives: de-chlorinator

What fish are in the tank, length, age, etc.
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3 red wag platies ( 1 male, 2 females), each is a little over an inch long
5 lyretail mollies ( 2 males, 3 females), maybe 8 inches total
2 emerald cories, approx 2.5 inches each

 

[Menagerie]

Ich...everyone's problem!
From what I understand, ich is always around--much like the little nasties that surround us. We wash our hands and take multivitamins and try to keep healthy. Our fish if stressed--due to poor water conditions, drop in temperature, overcrowding, changing tanks, changing tank mates, etc.--are more susceptible to ich.

 

[TankGirl]

Quarrantine for new fish is a great way to prevent disease. Fish get very stressed from shipping and sitting in less than ideal conditions at the LFS, so a couple of weeks of quarrantine will keep disease from spreading to your main tank.

Cory cats do not tolerate salt very well, so if you are keeping salt in the tank anyway for the livebearers it is going to be hard on those cory cats in the long run. When using heat therapy be sure there is plenty of surface agitation (leave the water level down just a bit so there is splashing) and/or add a bubble wall or something that will create turbulence at the surface to aerate the water. The higher temps reduces the available oxygen for the fish. Increasing water changes will also help cut down on stress related to water conditions, in general.

 

[jlindseyjr]

I've been trying to figure out what went wrong. Water params good, tank not overcrowded, temp stable. Only thing that changed was the addition of 2 female mollies. As far as the salt, I started with only 2 tbsp total. When I saw the spots, I added 2 more to bring it to 1 tbsp per 5 gal.