White spot on swordtail's head

[Blackaddder]

I noticed a white spot on my female swordtails head, behind her eye. She behaves normally, and the other fish seem fine (although 2 cory's suddenly died for no apparent reason a few days ago).

I have attached a picture (a bit blurred). Does anybody know what this is and what I should be doing about it?

Swordtail

 

[Red Tailed Wonder]

what are ur water parameters? what sized tank is she in? tankmates?



Info!

 

[Blackaddder]

29 gallon, together with 4 zebra danios, 1 panda cory, 1 male swordtail, 2 golden inca snails, 6 ghost shrimp, 1 cherry shrimp. There was a betta but he died of finrot.

Lately, there is 0.5 to 1 of ammonia, probably because of the antibiotic I used to treat the Betta. Nitrites are 0 and nitrates I haven't measured in a while.

 

[mandimoron]

Fin rot, coupled with an anomalous white spot says to me that your water quality isn't top notch-- get those nitrates tested! They may be higher than you think. >_o How often do you do water changes?

Is the spot kinda fuzzy lookin' at all?

 

[Blackaddder]

Ammonia: 0.5 to 1
Nitrites: 0
Nitrates: 5

I usually do 20% water changes once a week, but more often recently because there is some ammonia.