My platy just had babies. Is she done spawning or can she go back?

She may have had too many babies developing and sacrificed some eggs in order to have the rest of them develop properly. I would not upset her now by removing the eggs. I suggest you leave her in the breeder box until she has the rest of the babies. Ignore the eggs on the bottom of the box, It is likely that they will not survive. But Platys have young all the time, so it is not such a problem. She will have live young soon.

She looks like she may be pregnant. A female platy will become quite large when pregnant. Gestation lasts about 28 days. When she's ready, she will swim to a quiet part of the tank and give birth. The fry are fully developed and able to swim. If not removed soon, they may get eaten by the mother or other fish in the tank.

Chances are if your female platy was kept in an aquarium with male platys the likelihood of her being pregnant is very high. The general rule for keeping both male & female live-bearers in the same tank is a ratio of 2-4 females per male. The reason for this (which you seem to be experiencing) is that the male will become very persistent and chase the females around. Keeping more than 1 female will help alleviate some stress in your aquarium. Both the male and female platy will try to eat the young fry once they are born so you may want to confine the female to a “floating nursery” until they are born. Once the fry are born, remove the female and place her back in the aquarium. From there you can keep the fry in nursery (or move them to another aquarium) until they are large enough not to be eaten.

Both species are excellent "beginner" fish and quite easy to care for. Your 20 gallon tank is a good size for about 6 to 8 fish of this species. 10 would be close to overcrowding the tank. Once your tank is properly cycled, you can add your fish. They are omnivorous and will readily eat flake, pellets, freeze dried and live foods. Chemistry should be monitored regularly and kept as follows: ammonia 0ppm, nitrites 0ppm, nitrates 20ppm or less, pH about 7, water temperature between 76 F and 78 F. Provide moderate cover (hiding places). These fish are live bearers, so if you have male and female then expect fry (baby fish) at some point. If not separated, fry will likely be eaten by adults.

If the tank was not properly cycled before she went in, the water qualityu may be affecting her. Check the water parameters first. Temperature should range bewteen 68 F and 78.8 F (20C to 26C). Using a home test kit, ammonia and nitrites should read 0 ppm. Nitrates should be 40 ppm or less. Platys do best in a pH of 7 to 8.3. Adjust parameters as needed and see if it makes a difference in her behavior. Offer a variety of appropriate pelleted and flaked food as well as freeze dried to see if she has a preference. Platys are livebearers with a gestation of around 28 days. She will become noticeably bigger as her date approaches. If she is pregenant and has fry, you will need to separate her or give the fry plenty of cover in the tank. If not, she will eat them. The stress of a new tank and water may also be a factor. Hopefully, with some adjustments and different foods, she will perk up.

Keep her separate to prevent further damage. Maintain water quality via frequent water changes. Use only aged or conditioned water that is temperature matched to prevent stress or shock. Platys do best around 78F. Dissolve 1 teaspoon of plain aquarium salt (NOT table salt) per gallon of water in a cup of tank water and gently pour it into the tank. This will reduce stress, treat minor infection and aid in recovery. You can also add StressCoat or StressZyme. Treat with salt for 10-14 days then reassess fin condition. The fin should grow back eventually, then you can return her to the main tank.

In most normal circumstances, the guppy birthing process takes between two and six hours, but if the mother is having difficulty, it can take up to 12 hours for all the fry to be delivered. In some cases, the mother will deliver a few fry and then stop the delivery only to resume in a few days. So, give her a bit more time and try to not stress her out.