platy

Question
i have a red wagtail platy that has developed dark spots(not parasites) and now has got a crooked spine sort of hockey stick shape. he is still eating ok and swimming around but every few seconds swims to and lies on the bottom for a little while. Any ideas what i should do, all the other fish are fine. thanks for any help, Patrick

Answer
Patrick,
I have stated many times in my answers to various questioners that you can never truly tell whether a fish is sick just by looking at them.
They hide their illness as long as they possibly can, so testing water quality often is your best bet to make sure your fish are going to be as healthy as they look.
I suggest you test your water for ammonia, nitrites and nitrates, and make sure your temperature is correct. Being tropical fish the ideal temperature should be close to 79 degrees.
Your ammonia and nitrites should not go above 0, and your nitrates should not go above 20.
Make sure you are doing water changes every week, larger percentages for smaller tanks.
If you have a few platies then your tank should be at least ten gallons. Any smaller and they are not likely to thrive.
Dark spots are sometimes ammonia burns, and that is not a good thing. Make sure you are not overstocked, and read up on the nitrogen cycle.
Keep your water fresh and clean as much as possible for your sick fish.