Sudden Fish Death

My friend Red Tailed Black Shark suddenly died this evening and we have no idea why.
My friend has had his tank cycling for 2 weeks, with filter and heater running. He went to buy his fish today, and took in a sample of his water in too. The lady at the desk said that the water was fine for a fish. However it is now dead. Theres been no gill movement for about 20minutes. There is something strange about this particular fish though, it has a..sort of dark orangey lump on its stomach.
Any ideas as to why it died?

Ammonia.

uncycled tank

There seems to be another thread with the exact same topic, but this one has a picture of the "lump".
As I said in the other thread I don't think the fish died because it is an uncycled tank since it was just put in the tank today. From the measurements given I;m guessing it is a 20 gallon tank, that is plenty of water for the fish to be quite happy for a while even in an uncycled tank.

Are there any other fish in the tank?
Do you have a test kit to measure ammonia, nitrIte and nitrAte? (a liquid test kit, not test strips as they are unreliable)
Is there anything in the tank that is not made specifically for aquariums?

Rummynose said:

There seems to be another thread with the exact same topic, but this one has a picture of the "lump".
As I said in the other thread I don't think the fish died because it is an uncycled tank since it was just put in the tank today. From the measurements given I;m guessing it is a 20 gallon tank, that is plenty of water for the fish to be quite happy for a while even in an uncycled tank.

Are there any other fish in the tank?
Do you have a test kit to measure ammonia, nitrIte and nitrAte? (a liquid test kit, not test strips as they are unreliable)
Is there anything in the tank that is not made specifically for aquariums?

Click to expand...

I agree, we need to know if he dechlorinated the water and if it's possible any other toxins got into the tank. I really suspect chlorine first.

afremont said:

Rummynose said:

There seems to be another thread with the exact same topic, but this one has a picture of the "lump".
As I said in the other thread I don't think the fish died because it is an uncycled tank since it was just put in the tank today. From the measurements given I;m guessing it is a 20 gallon tank, that is plenty of water for the fish to be quite happy for a while even in an uncycled tank.

Are there any other fish in the tank?
Do you have a test kit to measure ammonia, nitrIte and nitrAte? (a liquid test kit, not test strips as they are unreliable)
Is there anything in the tank that is not made specifically for aquariums?

Click to expand...

I agree, we need to know if he dechlorinated the water and if it's possible any other toxins got into the tank. I really suspect chlorine first.

Click to expand...

I don't think that chlorine would have built up in the aquarium during the 2 weeks of "cycling", it is a gas and would have evaporated. Even if the OP's friend had changed the water before adding the fish, I kind of doubt that chlorine would have been present in such high amounts!?


Could the lump, be not a lump but an injury? Maybe the fish had gotten stuck somewhere and died of stress caused by the injury? Or a disease/infection not noticed in the store?
Another question: how long has the fish stayed in the bag after purchase until it was added to the tank?

Rummynose said:

afremont said:

Rummynose said:

There seems to be another thread with the exact same topic, but this one has a picture of the "lump".
As I said in the other thread I don't think the fish died because it is an uncycled tank since it was just put in the tank today. From the measurements given I;m guessing it is a 20 gallon tank, that is plenty of water for the fish to be quite happy for a while even in an uncycled tank.

Are there any other fish in the tank?
Do you have a test kit to measure ammonia, nitrIte and nitrAte? (a liquid test kit, not test strips as they are unreliable)
Is there anything in the tank that is not made specifically for aquariums?

Click to expand...

I agree, we need to know if he dechlorinated the water and if it's possible any other toxins got into the tank. I really suspect chlorine first.

Click to expand...

I don't think that chlorine would have built up in the aquarium during the 2 weeks of "cycling", it is a gas and would have evaporated. Even if the OP's friend had changed the water before adding the fish, I kind of doubt that chlorine would have been present in such high amounts!?


Could the lump, be not a lump but an injury? Maybe the fish had gotten stuck somewhere and died of stress caused by the injury? Or a disease/infection not noticed in the store?
Another question: how long has the fish stayed in the bag after purchase until it was added to the tank?

Click to expand...

I apologize, I should have made myself more clear. I was thinking that maybe the tank was never dechlorinated, but just left running. I've seen my LFS test water for people and they don't bother testing for chlorine. I know that Chlorine will dissipate, but I believe that Chloramines can last for the two weeks.

The lump is definitely something else to consider. I also agree that stress is high on the list of possible problems, maybe he just couldn't adapt to everything. I don't recall if the OP said if there were any other fish purchased that day. It's my understanding that Red Tail Sharks tend to be sensitive to water conditions.

I have one that seems to be thriving as he/she is nearly jet black with a crimson tail. That tank suffered a nitrIte spike for a few days after I slightly "over cleaned" the filter and changed the pad. He never acted like anything was wrong during that time, color never changed at all. I missed it, but I'm sure that there would have been a brief ammonia spike for about a day that preceded the nitrIte spike. He's starting to pick on my cherry barbs so he may be moving soon.