Maracyn's active ingredient is Erythromycin. The savings come in the large 24 pack or larger over the traditional API Erythromycin. Each packet treats 10 gallons.

Provides relief from bacterial infections such as body fungus, gill disease, fin rot and popeye in fresh and saltwater aquariums.

Mardel Maracyn® is a specially compounded broad-spectrum antibiotic (erythromycin) which has been shown to be effective against a number of pathogenic bacteria associated with ornamental fish disease. It was developed for complete but gradual dissolution in water. It is primarily effective against gram-positive pathogenic organisms. Symptoms of clamped fins, swollen eyes, heavy or rapid breathing, patchy coloration, change in swimming behavior or corner-hiding can be signs of possible bacterial infection.

All suspected bacterial infections should be treated immediately.

Mardel Maracyn® is non-toxic to invertebrates such as snails and shrimp. 

Don't confuse this with Maracyn 2, which isn't the same we don't currently carry.