That dang BGA!


Blue green algae. Photo from


Black beard algae. Photo from

Got blue-green algae problems? Who hasn’t at one time another. While there are many solutions for curbing its growth, this post is about a very effective yet quite underutilized solution for eliminating it. Often referred to as BGA, it’s not really an algae but rather a cyanobacteria.

I’m a bit of a purist when it comes to fish keeping. That means I’m reluctant to use most chemicals except water conditioners. However, because I’ve had my share of BGA in the past, I’ve become partial to using a common antibiotic typically used to treat bacterial infections in many invertebrates – Erythromycin.

You can Google the use of Erythromycin as an algaecide and you’ll find plenty of information. I don’t generally use chemical filtration in my tanks, but I’ve read that you can continue to use chemical filtration when dosing with Erythromycin. However, it won’t do any harm if you choose to remove your active carbon or whatever else you’re using.

As a side note, I’ve also had black beard algae (BBA) in the past. Though I’ve read that Erythromycin does not treat BBA, I have found this to not be accurate. I have dosed a BBA-laden tank with the antibiotic before, and it did significantly reduce the algae.

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