Hi - first thing to do - please test your tapwater for ammonia, nitrites and nitrates, and pH.
To solve this problem, water changes are the answer. Large daily changes, sometimes even twice a day depending on how high the levels rise how fast, but basically you change the water until there's no ammonia or nitrites. They're toxic to the fish, and any ammonia or nitrite levels that we can detect on our kits are causing some harm to our fish. When a tank begins crashing and fish are dying, their bodies begin to break down almost immediately, and produce ammonia. Other fish pick at and eat the body, sometimes eat them entirely - bacteria begin to break it down etc, so a large snail or a fish dying and us not finding the body for several hours, if at all, can lead to an ammonia spike.
I wouldn't use any other products except Seachem Prime as the water conditioner if you can get some. Use you current water conditioner for now. But Prime actually binds ammonia and nitrite for 24-48 hours, so it doesn't harm the fish, so it can help them to survive what's happening in between the large daily water changes you have to do to get the ammonia and nitrite levels under control.
But we really need to test your tapwater too, because if there's a problem with the source water, then water changing won't fix the issue, you know? So test that for ammonia and nitrite first with the API master test kit. If there's no ammonia or nitrite, then go straight to doing a large water change. As much as you safely can, since the more water changed for clean, non-toxic water, the better, since it will dilute any remaining ammonia. Again, water conditioner and temp match the new water to the tank temp like you did yesterday. Once that's done, let us know the test results and how you and the fish are doing! Don't feed the fish. They're fine without food for a week or two, so need to get this under control first, and food in= waste out and more ammonia. Fasting the fish for now won't harm them.
Search for fish bodies when you do the water change/substrate clean. The goldfish will have spiked the ammonia, but you said you couldn't see the molly, so if the body is still there, it'll still be producing ammonia, and needs removing. One of the platies is in bad shape too, and they're all stressed. Again, I'm so sorry you're going through this. Try to put emotions aside for now, and just focus on the tasks in front of you. Check tap water is safe, and if it is, large water change straight away, as soon as possible, to dilute out the ammonia and nitrite and try to save the remaining fish. Then come here to debrief and try to figure out how/if we can save the rest. Wish I was close by and could help!
To solve this problem, water changes are the answer. Large daily changes, sometimes even twice a day depending on how high the levels rise how fast, but basically you change the water until there's no ammonia or nitrites. They're toxic to the fish, and any ammonia or nitrite levels that we can detect on our kits are causing some harm to our fish. When a tank begins crashing and fish are dying, their bodies begin to break down almost immediately, and produce ammonia. Other fish pick at and eat the body, sometimes eat them entirely - bacteria begin to break it down etc, so a large snail or a fish dying and us not finding the body for several hours, if at all, can lead to an ammonia spike.
I wouldn't use any other products except Seachem Prime as the water conditioner if you can get some. Use you current water conditioner for now. But Prime actually binds ammonia and nitrite for 24-48 hours, so it doesn't harm the fish, so it can help them to survive what's happening in between the large daily water changes you have to do to get the ammonia and nitrite levels under control.
But we really need to test your tapwater too, because if there's a problem with the source water, then water changing won't fix the issue, you know? So test that for ammonia and nitrite first with the API master test kit. If there's no ammonia or nitrite, then go straight to doing a large water change. As much as you safely can, since the more water changed for clean, non-toxic water, the better, since it will dilute any remaining ammonia. Again, water conditioner and temp match the new water to the tank temp like you did yesterday. Once that's done, let us know the test results and how you and the fish are doing! Don't feed the fish. They're fine without food for a week or two, so need to get this under control first, and food in= waste out and more ammonia. Fasting the fish for now won't harm them.
Search for fish bodies when you do the water change/substrate clean. The goldfish will have spiked the ammonia, but you said you couldn't see the molly, so if the body is still there, it'll still be producing ammonia, and needs removing. One of the platies is in bad shape too, and they're all stressed. Again, I'm so sorry you're going through this. Try to put emotions aside for now, and just focus on the tasks in front of you. Check tap water is safe, and if it is, large water change straight away, as soon as possible, to dilute out the ammonia and nitrite and try to save the remaining fish. Then come here to debrief and try to figure out how/if we can save the rest. Wish I was close by and could help!
