An active ingredient in IchX is malachite green chloride which you reference in an old post.
Would moving these fish to another tank help? I’d have to use the same filters, a HOB & large sponge. Would they not contaminate the other tank? Will the ich on the fish reproduce in the new tank?
Yes, I’m hoping to hear from Andy & Colin. I’d hate to lose my sevs.
Let me start by saying that ick is more a symptom of another problem as much as a problem unto itself. Healthy fish usually easily repel the parasite. So you need to do some research on your aquarium as to why the fish succumbed as badly as they have. Something has them stressed.
Seeing the fish as covered as they are, it looks more like oodinium/ velvet vs ick. Ick will eventually get to that stage but it takes days for that to happen. With oodinium, that can happen within hours so treatment should be quick.
If the spots are larger and look like salt crystals, that's ick and malachite green is an effective treatment. IchX or Fritz product FIXICK should work as they both contain malachite green.
If the spots are smaller, that's velvet/ oodinium so the best treatment for that is copper sulphate. You can use Mardel's Coppersafe for this. You will need to also get a copper test kit that measures chelated copper so you dose the coppersafe to the correct level. This is a 10 day treatment and there may be items in your tank that can absorb some of the copper out of solution. You also want to turn the lights off and keep the tank as dark as possible as velvet photosynthesises the light for food. You should also raise the temperature to at least 82-84 degrees. Be sure to increase aeration as the higher temperature will reduce dissolved oxygen levels in the water.
There have been some good results with doing saltwater dips of the fish but if it's an advanced stage, it's better to add salt to the tank than stress the fish with capturing it/them to dip it/them. All the fish in the tank may have some stage of the parasite so all fish need to be treated.
If you are unsure which it is, go to this link:
https://www.monsterfishkeepers.com/forums/threads/fish-disease-pictures-and-info.626692/ and about a third of the way down will be pictures of both conditions for you to compare.
If you are still unsure, I'd treat with the coppersafe, heat and darkness. Malachite green will kill ick but not oodinuium. Coppersafe will treat both but is a harsher treatment so used more carefully.