fish medicine

Question
i have guppies in my tank, and it's been set up around 2 months
now.(it's a 10 gallon tank). i had 8 guppies, but 5 of them died
in the same week and a half (a week and a half ago), so now i
have 3 left. i went to a fish store so they could check my water,
and they said my pH was WAY to low. so he told me i should get
this medicine for my fish(triple sulfa capsules) because he
thought they had fungus on they're tails. but i told him i had
babies in my tank too,(in a breeding tank, but it was inside the
big tank) and they weren't dying, only the adults were. so i asked
him if it would kill my baby fish if they didn't have they fungus,
and he said he didn't know, and if it did, i had to decide. so i'm
not sure if i should put in the medicine or not, because i don't
want to kill my babies. will the medicine hurt the fish that aren't
infected? (i checked google please don't tell me to look there)

Answer
Hi Hillary,
 A couple of things.. first go to a different fish store :)
I am always suspicious of fish stores that recommend that you add a bunch of nasty chemicals to a tank when they aren't even sure what the problem is.  In many cases, the medicine is worse than the problem.  

 First, guppies don't care about pH.  They are extraordinarily tolerant of water type so you don't have to worry about that.
What you do need to worry about is that their water must be clean.  Are you doing regular water changes?   You should be changing about 20% of the water ONCE a week, EVERY week.  Don't change more than that at once or you will shock the fish.  And do it once a week and your fish will be happy.  

 The fact that your fish have had babies and that the babies are doing well suggests that things can't be too bad in the tank.  And yes, things like sulfa medicines can be particularly hard on baby fish so I wouldn't use them.

 Never treat fish as a preventative. Only treat what you clearly know to be wrong, e.g. a clear case of ick or something like that.  Otherwise, your tank will become a toxic soup of chemical residues and the fish won't be any healthier, plus they will become immune to the medicines and the medicines won't work when you really need them.

-- Ron
  rcoleman@cichlidresearch.com
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