Maracyn 1 and Marcyn 2 questions

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Aquarium Advice Addict
Apr 26, 2006
Clearwater, FL
I've had terrible losses in my tank since setting it up. A bacterial infection is suspected - just lots of "mysterious fish deaths" (see thread in General Discussion I'm going to treat with both Maracyn 1 and Maracyn 2 to try and stop the deaths.

I have a few questions:
1. Will it kill by bio-filter ?
2. Are these safe for my mystery snails ?
3. Are they safe for live plants ?

Thanks ..... hopefully I can stop the fish losses - I can't take this heavey heart of mine much longer :cry:
Both claim to not affect the biofilter, but watch for an ammonia spike just in case. Your snails should be fine. Your plants will only suffer from reduced light because you should reduce the amount of light on the tank because maracyn 2 is light sensitive.
Thank you so much for the response. Its a low light tank so I'm not too worried about them but I'll keep an eye out just in case. I'll try to dose at lights out so that there's a long period of initial time in darkness.
I've used Maracyn 1 in a planted tank and I did get a small ammonia spike (.25 ppm) but it quickly resolved itself. At the end of treatment, I did about a 40% water change and used carbon to remove the meds. The plants were not harmed at all.
Thanks. The packaging says that both are ok for inverts but they don't mention plants ! Isn't that annoying ??? Since I haven't even planted the tank yet (the plants arrived today - I'm planting tomorrow) I do hope they survive. The packaging certainly doesn't say "do NOT use with live plants" so I'm hoping its ok .... if not, well - I guess my plant lady will just get another order from me .... I've spent so much money on this tank whats another $100 !
I probably put more maracyn in the tank than what is recommended for fish (fish were not in the tank at the time). I was trying to halt a cyano outbreak and I added the meds, plus did a whole tank blackout (wrapped with several layers of newspaper). When I lifted the newspaper I think the plants were actually bigger! So IME, you don't have to worry about the plants at all - just concentrate on getting the fish better! The plants will come through just fine.
Maracyn, (Erthromyacin), at half dose, will normally get rid of cynobacter, even without blackout. In my opinion, that is about the only use for it in a FW tank. It only works on gram positive bacteria, and it seems that most bacterial infections are caused by gram negative bacteria. Maracyn II is minocycline, which is in the tetracycline family. Tetracycline drugs are affected by calcium, so if the water is hard, the dosages need to be increased. Before any treatment a large water change is in order.
Thanks Bill. I did a large water change today and planned on starting treatment tonight. And I do have hard water .... the packaging didn't say anything about increasing the dosages so I'm at a loss at how much to increase the dosage by.
I just want to KILL whatever it is that's killing my babies LOL
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