API E.M. Erythromycin


This is what we use here at the store and at Cory's fish room to treat every fish we come into contact with. For us we've never had problems using it with inverts, scaleless fish, and plants. We've never had our beneficial bacteria die from this medication, but as with all medications take precautions in case your cycle does crash. 

Commonly used to treat:

  • Cyanobacteria
  • Fin Rot & Tail Rot
  • Columnaris¬†
  • Open Wounds

Dosing Instructions:

For best results remove activate carbon. For each 10 gallons of water empty on packet directly into aquarium (For 850gm jar, add one scoop [1tsp] per 20 gallons), repeat dose after 24 hours then change 25% of the aquarium water. Repeat treatment a second time for a total of 4 doses, then make a 25% water change. Treatment may be repeated if necessary. Four doses required for full course treatment. 

Treats 100 Gallons. 10 Packets, each treating 10 gallons. 850gm container treats 3270 gallons.



Customer Reviews

Based on 50 reviews
Mind At Ease!

Thank you Team Aquarium Coop for testing all these meds and posting a great video on them! It is great to medicate my tank before any fish get sick, and have all the info i need to do it in one place!

Value & Convenient

Much easier to dose larger aquariums with the provided scoop. I prefer to have this on hand for fish and algae emergencies.

It works

Not sure what else to say other that it works. I use it as part of the quarantine trifecta. So far, so good.

Easy to use

The instructions are easy to understand and it seems to do the job!

Expensive, but well worth it!

This is my go to product for bacterial treatments. Not sure why API has switched to Furan-2 and others that do they same thing as EM but not as effectively. I bought the 850 gram container to be well stocked. Wish I could buy more, but cannot justify it to the lady of the house. Aquarium Co-op shipped it out quick even through all the BF/CM busy-ness.

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