Losing fish

[Country joe]

Need pictures and video of the fish.

Why did you change the filter media?
You only replace sponges if they start to fall apart and that doesn't normally happen until they are 10+ years old.

How long have you had the rummynose (a couple of days)?
If you have had the rummynose for less than 2 weeks, do not do any water changes for a couple of weeks, then only do 10% water changes once a week for a few weeks before increasing it to 20% for a few weeks.

Rummynose tetras have issues at certain times of the year and just drop dead for no reason. They show no signs of disease and just die. This is caused by either water chemistry changes or drug overdose. If the fish are wild caught they can be kept in really soft acidic water at the collectors (pH below 5.0 and a GH of 0ppm). If the suppliers have them in water with a higher pH they struggle and die. When the shops get them they usually end up in water with a higher pH again and the fish just die for no real reason. They will normally settle down after a month or so but you need to be very careful during this time because any sudden change can cause them to die.

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The drug overdose is from the suppliers and importers who treat the fish for everything because they are dying. They don't normally need treating and are dying because of a sudden rise in pH. The fish get weak from the chemical exposure and up and die for no apparent reason. Part of it is the fish's immune system is stuffed due to the chemicals and the fish can also become addicted to the chemicals and need them to live otherwise they go into shock and die.

The fish can survive the drug problems but they need to be kept really calm for at least a few weeks (preferably a month or more). This means low light and no water changes, and nobody going into the tank or stressing the fish in any way. We used to have the lights on but half to two thirds of the tank was covered with thin sheets of wood to stop any light getting into it. After a couple of weeks we allowed more light into the tank and over the next month we allowed more in.

You also need to turn the room lights on or open the curtains at least 30 (preferably 60) minutes before turning the tank lights on.

Thanks Colin, I changed the filter media over, as I purchased a fluval 407 and changed over from my 307.
Would dimming the lights for a few weeks, affect my plants

 

[Colin_T]

Reducing lighting does adversely affect the plants but the fish (if they are wild caught) will do better in a darker tank with a lower pH and maybe add some tannins.

Still need pictures and video to confirm no diseases. But we had lots of issues with rummynose tetras around this time of year when we got them into the shop and it was pH and chemical related. Hopefully that is the problem and they just need time to settle down.