Columnaris treatment and the nitrogen cycle

[Boven]

Not long back I purchased a couple new female sunset platys to better balance out the male-female ratio in my 38 gallon tank.  For the first day or two they both kind of hung off by themselves among the plants.  Soon one of them was up and swimming about with all the other fish, but the other tended to stay off to herself.  She came up for feedings and seemed okay otherwise.

Since she was eating (she'd zip right to the top at feeding time or when I'd move around in front of the tank) and otherwise seemed okay, I figured it was due to her being a 'new kid.'  Also, one of the male platys has been a bit more aggressive lately, resulting in some nipped fins and a couple missing scales on one of the other males. I suspected that he might be picking on the new girl, too.

Saturday, morning I noticed her face looked downright white.  At first I thought it was just he light since she's such a bright yellow to begin with, but then realized she was holding her mouth open a bit, too.  She was down among the plants so I shooshed her out with a net to get a better look at her and confirm what I thought I'd been seeing.  She was swimming normally, but her face was definitely white and mildly cotton-looking and she was, indeed, keeping her mouth well opened.  Since this seemed like it must be columnaris, I went out and got some Maracyn and Maracyn 2.  In the short time I was gone, though, the platy had died.

Of course, this led me to trying to get a good look at everyone else in the tank.  While the one female might've just been stressed out enogh to let it take hold, I wanted to be sure the others were looking okay.  I didn't see any obvious white patches on anyone but thought I could see a spot or two on a couple of the other platys.  It's hard to tell with their light color.  To play it safe, I figured I'd run a course of Maracyn and Maracyn 2.

On top of all that, when I went to do a partial water change in order to ensure the environment was as ideal as possible before starting the meds, I spotted two brand new fry hiding; one among the plants and one under the pleco's driftwood 'cave'.  I don't know who the mother was. None of the females were any fatter than usual lately.

After all that long backstory, I finally get to the questions at hand:  Will the medication mess up the nitrogen cycle in the tank?  If so, is there anythign I can do to lessen the impact of it?  Seeing as how I can't catch the babies (fast little boogers and they even hide among the gravel), are they likely to survive the treatment, assuming someone doesn't eat them?

[wendyjo]

Any med that contains an antibiotic has the possibility of killing off the good bacteria in your filter.  You really just have to test the water often and do water changes as needed until things balance out again.

This is exactly why you should ALWAYS quarantine new fish and plants.