Do I have a sick fish?

[raydobbs]

Yes, that does sound like pregnant animal behavior.  I might get a breeding trap or such to put the fish in for a bit to see if that's what's wrong.

If it's always been acting this way - and it's not pregnant, then it might be experiencing stress and some illness - keep an eye on it, monitor the conditions carefully - and consult your local fish store (not a pet superstore, but an actual aquarium shop - pet superstores don't train their people enough)  If you make any change to the conditions of the tank - then make them GRADUALLY - otherwise, you will have a lot of dead fish.

[imnew]

I just started my tank about a week ago.  I have 5 Platies.  One has been keeping to itself, usually hiding in the rocks or corners of the tank.  Is this normal behavior or do I have a sick fish?  It doesn't look any different then the other four, it has iss acting different.

[edpaff jr]

It may be pregnant.  This is what my platy does before she has her fry.

[fishtankgrandma]

If the tank has been only set up a week, my guess is you probably have high amonia readings. Do a 50% water change and add some stress coat. When in doubt of what's wrong, do a big water change and vacuum the gravel. 99% of the time it's what we do to make the fish sick. We feed them every time we go near the tank cuz they come rushing over to us and we think they are hungry.
I had platies as my first fish. I loved them. I fed them and fed them and then wondered why I ended up with some big platies with bacterial infections. My how I learned. After medicating a lot of fish to death, I learned to do BIG water changes every week or more if necessary. That took me nearly a year. I still feed too much, but you know how it is, they really are hungry. Right.