On the assumption you are a fairly new aquarium keeper, I will explain something about this approach. It is in fact the wrong way to go. Prevention is always better with fish, rather than risking something. For one thing, a "cure" may not be possible, but even more importantly is the fact that any and all substances added to the tank water do get inside the fish and this can damage them internally and they will at best be weaker going forward. Medications should never be used, ever, unless you are fairly certain of the issue, and then only if the medication is the most effective and safest. It is very easy to kill other fish just by using this or that substance.
Iridovirus is not treatable. Dwarf gourami seem especially likely to carry this, so unless you absolutely know the breeder from where the fish came, do not acquire them. The virus can be carried and passed to other fish even if the host fish does not show any symptoms.
A better gourami and one that is very similar, and more peaceful as well, is the Honey Gourami.
The iridovirus may or may not be transferable to species other than the Dwarf Gourami. Some very experienced sources think it is, others are skeptical. Risk is not the way to go with fish.
