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- Dec 13, 2018
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Did you treat your fish with anything before adding it to the tank? If it had internal parasites or any diseases it could have easily died of that and passed it to other fish. The fish could have lived with it for a while and eventually succumbed.
Or, your nitrogen cycle wasnt complete when you started the tank (if you are using faulty test kits- how would know?) And you have only been keeping levels down with water changes and once you added another fish it overcame the delicate balance you had going. If you just started the tank about 6 months ago and put a bunch of fish in a month after (including a mandarin- which usually need more mature tanks) I would guess that you overstocked before your nitrogen cycle could catch up and ammonia has been slowing building up. Hard to tell.
1. Test the ammonia with a better kit, plain and simple.
2. Do a water change if needed for the ammonia and get media that absorbs it.
3. Let the tank rest with no new additions for a while until it stabilizes- like 3 months.
Or, your nitrogen cycle wasnt complete when you started the tank (if you are using faulty test kits- how would know?) And you have only been keeping levels down with water changes and once you added another fish it overcame the delicate balance you had going. If you just started the tank about 6 months ago and put a bunch of fish in a month after (including a mandarin- which usually need more mature tanks) I would guess that you overstocked before your nitrogen cycle could catch up and ammonia has been slowing building up. Hard to tell.
1. Test the ammonia with a better kit, plain and simple.
2. Do a water change if needed for the ammonia and get media that absorbs it.
3. Let the tank rest with no new additions for a while until it stabilizes- like 3 months.