Just to educate a bit about why people are recommending Furan-2, bacteria can be gram positive or gram negative. Many anti-bacteria treatments available only treat one or the other. When you are unsure of what is effecting your livestock selecting medication that deals with both is the best way to cover all possibilities. If for some reason you are unable to find something like Furan-2 make sure you get other medications that either deal with both or buy two different anti-biotics that cover both gram positive and negative.
I have had excellent luck over the 10 years I kept seahorses with treating diseases as long as I had the proper medication on hand to begin treatment in a hospital tank once I detected a problem. Just remember that the medication expires so you need to toss the old and buy new every 2 years or so. The only time I wasn't able to handle the issue is when one of my males got internal gas bubble disease, I had to take him to a specialty vet to get Diamox for him, which I learned you can get in liquid form, shrimped flavored.