Where to buy
Fritz 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 is primarily effective against gram-positive pathogenic organisms.
Active Ingredient: Erythromycin
For the treatment and control of columnaris “cotton wool disease,” fin and tail rot, popeye and gill disease in freshwater and saltwater fish caused by Flavobacterium columnare, Haemophilus piscium, Aeromonas punctata, Aeromonas hydrophila and Cytophaga aquatilis bacteria.
Columnaris “cotton wool disease”
Popeye
Fin and tail rot
Gill disease
Also helpful against mouth fungus, open lesions, hemorrhagic septicemia, and slime disease.
Consult a veterinarian or fish expert for assistance in diagnosis of disease-causing organisms and treatment options.
All suspected bacterial infections should be treated immediately.
Symptoms of possible bacterial infection can include clamped fins, swollen eyes, heavy or rapid breathing, patchy coloration, change in swimming behavior or corner-hiding.
Greyish-white stringy material covering most of the body; white or gray patches
Protruding eyes, may be cloudy or hazy
Swollen, discolored gills, gasping for air and a decrease in activity
Split, ragged or deteriorating fin and/or tail
Add the contents of one packet per 10 gallons (38 L).
Repeat dose daily for five days total
Treat for five days even if signs of infections disappear
On day six, perform a 25% water change
Monitor ammonia and nitrite levels daily
If symptoms improve but do not completely disappear, repeat five-day course once more.
May be safely used along with other treatments: Coppersafe, Maracyn Two, and Maracyn Oxy.
Dividing up our powder packets accurately for use in smaller tanks can be tricky, and to get the proper dose we recommend making a concentrated solution that is much easier to measure, see video below
Treatment may inhibit nitrifying bacteria. Monitor ammonia and nitrite levels during treatment.
Maracyn is compatible with many fresh and saltwater species, equipment and most Fritz products, see below for details.
Species | Compatible? | |
|---|---|---|
 | Saltwater fish |  Yes |
| Freshwater fish | Yes |
| Snails and other invertebrates | Yes |
| Koi and goldfish | Yes |
| Live plants including pond plants | Yes, some plant species may show temporary yellowing |
| Bettas | Yes |
| Coral | Yes |
Equipment / Products | Compatible? | Notes | |
|---|---|---|---|
 | FritzZyme Nitrifying Bacteria | Yes | Always monitor water quality and re-dose FritzZyme after treatment to restore biological filtration. |
| Fritz water conditioners | Yes | |
 | Maracyn Two | Yes | Safe to use at the same time |
| Maracyn Oxy | Yes | Safe to use at the same time |
| Coppersafe | Yes | Safe to use at the same time |
Here are our most frequently asked questions about Maracyn.
Ask our experts, we’re here to help!
| Item # | Size | Case QTY | UPC |
|---|---|---|---|
| 75046001 | 10 Powder Packets | 24 | 080531460016 |
| 75046002 | 20 Powder Packets | 12 | 080531460023 |
