Used Esha 2000 and Esha Exit with snails and shrimp quite a few times without any harm to them as I think you will find @Guest has.eSHa 2000 is a combination of a gram positive antibiotic, some antiseptics and copper. The last will kill any shrimp and snails.
We don't know that for sure, so my advice would be to go ahead and treat and hopefully Harry's Gourami will make a full recovery.Dwarf gouramis are often infected with an iridovirus
Abstract
Mycobacteriosis is a common cause of chronic ulcerative skin disease in aquarium fish that can be difficult to treat. This case report describes the use of injectable enrofloxacin (0.23 mg intraperitoneally three times weekly) in the treatment of mycobacterial infection in three aquarium fish (two angelfish and one gourami). The fish were treated for a total of 12 to 14 weeks. One fish initially improved, then died after 12 weeks of therapy from presumptive central nervous system mycobacteriosis. The other two fish were cured of infection after 14 weeks, suggesting that enrofloxacin may be a useful treatment for piscine mycobacteriosis.
3. Enrofloxacin (Baytril®). A quinolone compound that appears to be safe and effective in fishes. May be used IM, ICe and PO at a dose of 5-10 mg/kg/ Q 48 hours for 7-21 days. May be diluted with sterile saline since the concentrated form (2.27%) may be irritating. May also be used as a bath at a concentration of 2.5 mg/L for 5 hours Q 24 hours. Recent work (Lewbart et al., 2005) indicates 10 mg/kg ICe Q 5 days for koi at 20 degrees C.
Dwarf gouramis are often infected with an iridovirus, the appearance of sores is a known symptom. There is no treatment.