Sure. I used antibiotics that are commonly used in research laboratories for cell culture. I am not sure if they are generally available in the forms that I used them, but...
To 500ml of seawater from my tank I added:
5ml of a penicillin/streptomycin combination (1:100 dilution)
0.5ml of gentamycin (1:1000 dilution)
Following a 20 minute dip in the antibiotic solution, I placed the ricordia back in the tank and discarded the antibiotic solution.
This seemed to halt the "melting" of this ricordia that had completely destroyed another specimen in just a few days. If I remember correctly, only one treatment was necessary.
That this worked so effectively may indicate that the melting was due to a bacterial infection. I was really just giving it a shot in an effort to save it.
Other broad spectrum antibiotics that are available in the fish disease section of pet suppliers may work similarly. Just make sure to perform the treatment outside of the tank and not to add the antibiotic solution back to the tank water. I didn't think that the small amount of residual antibiotic that remained on the specimen when I returned it to the tank would be concentrated enough to harm the beneficial bacterial population in the tank.
