Mysterious Deaths

Question
Hello

I have an established tank that had 3 platys in. I had had them for about a month when one gave birth. Most of them were eaten and I am left with 3 fry. A few weeks later the female who gave birth died. The other fish seemed OK so I bought 5 guppys. Then following day 2 of the guppies died. The day after that, both my platys and another guppy. Now I looking at a guppy hanging at the suface - I've read it could be lack of oxygen so I put an oxygen tablet in.

I had to clean the whole tank out - there were bits of dead fish and I thought it might be a bacteria killing them. I only read online afterwards this is what you shouldn't do.

One death is bad luck but there is obviously something wrong - I've added chemicals to make the water safe and also one for stress coat.

I really don't want to lose any more fish - especially my fry! (which seem ok at the moment)

Thank you for you time and help.

Answer
Hi Charlotte,
 You should not clean the whole tank out, but you should definitely do a 25% water change after any fish has died in a fish tank.  

 An oxygen tablet isn't going to have any meaningful effect on a fish tank for very long. Do you have a proper filter and airstone in the tank?

-- Ron C.
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>