To begin with, you'll want the temperature around 80 to 82 degrees,and 0 Ammonia, 0 Nitrite, and Nitrate of less than 20. Please see mynote below on keeping sufficient numbers of both guppies and platys tolessen stress on the females, keeping in mind that a tank which is atleast 20 gallons is really best for keeping these fish in propernumbers. Now, on to what's going on with your fish: you describethe string as being on the tail, but then mention both eggs and poop,which certainly wouldn't be on the tail, but rather, the undersideof the fish, so I'm unclear on where the problem is. If allyou're feeding is dry fish food, your fish could be suffering fromconstipation or other issues, and it's always a good idea to feedwet-frozen foods along with dry foods, anyway, to provide more varietyand promote digestive health. If the string is no longer hanging, andthe fish is pooping normally, then it was likely nothing to worryabout, but do research the fish you're keeping and ensureyou're providing the necessary space, water conditions,temperature, etc. to keep them healthy.>
I searched it and found answers of (for highest temp) 90F, 76F, etc
First, put the adults back in the tank. They will get sick and die in the bowls--they need filtration and heat.
Second, some options for the fry. Try to catch them and put them in a breeder box or small filtered, heated tank. Or, add lots of hiding places--java moss or plastic breeder grass works well, since they can get down in the tiny spaces away from the adults. Or, use a divider to separate the adults from the fry.
Third, if these fry don't make it, don't worry too much. Platies are prolific breeders and will produce many more babies for you. Some will be eaten, but if you provide lots of hiding spaces, chances are some will survive. Make sure you have a plan for housing any survivors. Numbers will increase quickly and you could be overstocked in short order.
Platy fry can eat regular fish food--crush it up into powder before feeding. Temperature should be the same as for any tropical fish--about 78 degrees. Lighting does not matter unless you have plants.
My tank with the heater on and lights off is steady at 81F
: It’s good that your trying to take proper care of your new fish! Platy fish do need a heater in their tank. When buying a new heater figure on needing 5 watts of energy per 1 gallon of aquarium water. You need your water temperature to stay in the range of 74-82 degrees Fahrenheit.
The Right Temperature To Keep Mollys And Platys | My Aquarium Club