Help me, fish experts! After maintaining a clean, happy tankful of freshwater fish for a several years now, I recently introduced a few new glo-light tetras and a bad ich infestation. (Don't bother berating me for being lazy and not quarantining the new guys, I've already beat myself up about it pretty thoroughly.)

All of the tetras (old and new) succumbed to the infection, but after about 10 days of treating the water with ich medication, and then 3 days of an anti-fungal medicine, the remaining huge goldfish is finally looking and acting normally again (whew!). The only other fish in the 20 gallon tank is an albino cory who never showed signs of disease or stress during the entire ordeal.

It's been exactly 3 days since I removed the last tetra (who still had white spots up until his death) and stopped medicating for ich. Is there any possibility the parasites might still be lurking in the tank after 10 days of half-dose treatments? The temp is right at 70°F (no heater), and the pH is very slightly acidic (can't remember the exact number). Everything I've read about ich seems to indicate that it can survive weeks, but the surviving fish haven't had any spots for a week or more, and the medication was really taking a toll on the goldfish. :(

Should I be concerned about re-infection at this point?

Hm. Well, from everything I was taught, you should not mix tropical fish with goldfish. I've seen a few people do it, but they had huge tanks and they were pretty seasoned fish owners. Even then, though, I didn't think it was something to do. So, you might want to think about putting the goldfish in a different tank entirely.

How many fish do you have in the tank? Are any of them full grown?

You could try doing a 25% water change and see where you're at after that.

We've actually had tetras for quite some time before my kids brought home the goldfish a year ago (%&#$ (%@&#$)! carnival games!), but all of the fish were doing pretty well together until I stupidly added the new ones. :dunce:

Right now, it's just the big goldfish and one (fully grown I think) albino cory in a 20 gallon tank. The water change today (and return of the carbon filter) was helpful I think, since it removed some of the anti-fungal medication, and the goldfish is acting much MUCH better now. I won't be adding any new fish for at least a couple months, until I'm sure there's nothing contagious in the tank.

Ich :gun:

The temp on the tank needs to be raised to 78 to 80 to kill it. You need the heater on. I would remove all fish for like 4 days.

I probably wouldn't add anything else to the tank, a full grown goldfish needs at least a good 15 gallons of water because they're such high waste fish, and then with the cory at adult size you can follow the 1 gallon/inch rule, so about 2.5 gallons. That only leaves you about 2.5 gallons of "extra" water and with the gold fish in a tropical tank I think it would be a bad idea to stock it to capacity. The presence of the goldfish probably contributed a lot to the death of the tetras and the severity of the ich infestation, and if any new guys do bring a disease it will be hard to treat because the tropicals need pretty high temps to boost their immune system, which could cause the goldfish to suffocate.

The temp on the tank needs to be raised to 78 to 80 to kill it. You need the heater on. I would remove all fish for like 4 days.

This will work, or you can treat it with an Ich treater. We had a horrible infestation not too long ago, almost whipped out all of my swordtails. But we got some of the water treatment and it cleared it right up.

Another good way to treat is ich is by adding a tablespoon or two of aquarium salt per 5 gallons of water. I've never had the bluewater ich treatments work for me. You can also add some aquarium salt to your tank when you put your fish back in as prevention.

Thank you for all of the info and suggestions, everyone!

As for ich treatments, I'm basically stuck with the commercial medications because the cory can't tolerate salt, and both fish don't do well in heated water. And if that wasn't enough, both tetras and catfish are sensitive to the medication, so I could only use half-dosages. arrrggh! :juggle:

Anyway, I think I'll take the advice from thebelovedtree and not add more fish at all. So far, both inhabitants are looking and behaving normal now, so I'm going to cross my fingers and watch them closely!

Thanks y'all!