Why is my new platy fish not eating, hiding, and pooping red?

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.

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.

Thanks for reaching out about your fish. Most of the water additives don't get absorbed systemically since fresh water fish do not drink water. A veterinary visit with a fecal sample is recommended to identify possible parasites and then prescribe a treatment. Most likely the medications needs to be top-coated on food and then eaten. Dosage depends on number of fish and estimated biomass (cumulative weight of fish). Good luck.

Check water chemistry using a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence (0 ppm) of ammonia and nitrites with nitrates at 20 ppm or less. Perform partial water changes, if necessary, to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. Check the temperature as well. Low temps can affect appetite and activity in fish. Once water parameters are stable, she may begin to eat again. If not, you can soak food in a bit of garlic juice to stimulate the appetite and provide a boost to the immune system.

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.

Some platys will have black spots on their bodies. This is normal and no cause for concern. Monitor for lethargy, decreased appetite, rubbing on objects or "flashing" (darting about the tank). Check water quality and chemistry. Make sure ammonia and nitrite levels are at 0 ppm (parts per million). Nitrates should be less than 40 ppm.

Check the water temperature. Low temps can affect appetite and digestion in fish. Angels do best between 78 F and 80 F. You can soak food in garlic juice to stimulate his appetite. Next, check the water chemistry. This can be done using a home test kit or by submitting a water sample for testing. Most pet stores will do this for free or for a small fee. Confirm 0 ppm ammonia and nitrites with nitrates at 40ppm or less in a tank with live plants or 20 ppm or less in an unplanted tank. Partial water changes can be done, if indicated, to stabilize chemistry and/or maintain water quality. use only aged or conditioned water that is temperature matched to prevent stress or shock. Although they do best in slightly acidic and soft water, they are quite adaptable. Fast him for 2-3 days then feed bits of cooked and shelled green peas. if he is constipated then this should him him get regular again. A broad spectrum parasite medication, such as PraziPro, should be considered. You can find it in the aquarium section of the local Petco. Follow label directions carefully.