Cardinal tetras dropping like flies

PLEASE HELP!
On Friday I bought some new fish for my tank. In my 10g tank I put 10 cardinal tetras and 3 balloon moollies to quarantine before adding to my main aquarium.

2 days ago one of the cardinal tetras died,yesterday another one, and today another 2... The only thing that seems weird about them is that their tail fin is frayed. Also the second one that died (it was the only one I saw dead, the others died while I was at work and my parents got rid of them) seemed to be kinda dark(?) in it's upper body above the stripes.

I really have no idea what's wrong. Please help!

 

Well what is the temp, nitrate, ammonia and nitrite of your qt tank ?

 

Thing with cardinals is they just are’nt strong fish. I bought 8 earlier in the year and all were dead within a month. Just poor shipping. These fish from caught to your tank are not fed. So your talking 3-4 weeks without food. So your getting weak fish to begin with.

 

Also, what is the pH and water hardness in your tank.

Mollies are brackish water fish that like water than is higher in pH, fairly hard and slightly salty.

Many cardinal tetras are wild caught from South American waters that are low in pH (acidic) and low in hardness. They won't like salt. Some cardinals are tank bred and might be more likely to acclimate to hard water. Wild caught fish might not do well in hard, alkaline water.

Thus, no matter what your water conditions, it is likely that either the cardinals or the mollies will be stressed. If your water is moderately hard and slightly alkaline, the combo might work.

There are many fishkeepers who make the mistake of trying to keep fish together that are not compatible in size, temperament, and water parameters. I have made such mistakes several times in the past, but have learned from my mistakes. Unfortunately, when you purchase fish at your LFS, they rarely tell you that the fish you plan to purchase may not be suitable tankmates.

 

I'll check the parameters when I get home.. Also I got the fish from a store and not shipped, I kinda doubt they weren't fed...

 

You might ask the store how long they have had them before selling them (the store received them via shipping); you could also try asking if they are tank bred or wild and if other customers have had issues with cardinals dying.
-
I've had mixed success. I have some that are 2+ years of ownership and others that never really adapt. Mostly i find that if i can get them to live a week they are fine but it helps that i have a group of 20 that can show the new ones the ropes.

I'll check the parameters when I get home.. Also I got the fish from a store and not shipped, I kinda doubt they weren't fed...

 

Balloon mollies can be bullies as well, especially if they are derived from Velifera. If your cardinals were weak to begin with, mollies may have harassed them to death.

 

Thing with cardinals is they just are’nt strong fish. I bought 8 earlier in the year and all were dead within a month. Just poor shipping. These fish from caught to your tank are not fed. So your talking 3-4 weeks without food. So your getting weak fish to begin with.

Where did you get that info ?

 

I'll check the parameters when I get home.. Also I got the fish from a store and not shipped, I kinda doubt they weren't fed...

the thing is, they were shipped to the store. If the store just got them in it is possible the stress of being shipped to the store and all they go through before we put them in our tanks is more than they can take.

They are netted and put in a bag, stuffed in a box and shipped to the store. Then they are dumped into a tank and before long we buy them. Often the same day they get to the store. They are netted again, put in a bag again and we bring them home. It is a miracle that any of them survive with all they go through to get to us.

 

the thing is, they were shipped to the store. If the store just got them in it is possible the stress of being shipped to the store and all they go through before we put them in our tanks is more than they can take.

They are netted and put in a bag, stuffed in a box and shipped to the store. Then they are dumped into a tank and before long we buy them. Often the same day they get to the store. They are netted again, put in a bag again and we bring them home. It is a miracle that any of them survive with all they go through to get to us.

Isn't that the story of every fish ?

 

Where did you get that info ?

Fish dying was my experience. The shipping was either here or another site. Also here once they reach the lps most still don’t feed them. First food is usually by the buyer. This didn’t come from one answer but most answers

 

Isn't that the story of every fish ?

Yes it is.

 

Fish dying was my experience. The shipping was either here or another site. Also here once they reach the lps most still don’t feed them. First food is usually by the buyer. This didn’t come from one answer but most answers

As this would be the case it would count for almost all fish. Mynexperiences over the years with cardinals is quite different though. Cardinals were wildcaught for a long time and appeared to be even more hardy than earlier tankbred fish (like neons). Nowadays a lot of cardinals are tankbred as well. I hardly ever see skinny / starved cardinals.

Three months ago in Bonn Germany.

 

Three months ago in Bonn Germany.

I know that these are in fact tankbred, because the store has a policy of not selling wild caught fish.

 

Cardinals are the fish I have technically had the best luck with. I bought 18 about a year and a half ago and have 15 left. Healthy as horses. I have issues with Neons and Rummies. I just look at them, or move 1 rock and it's like ahhhhh everbody die

 

I know that these are in fact tankbred, because the store has a policy of not selling wild caught fish.

But as said the wildcaught ones were believed even hardier.

I liked the quality of these. Probably Czech Republic ones then at Freßnapf

 

I picked up 6 wild ones back in early July. One died last week The other 5 seem fine. Not sure why it died but maybe an angel harassed it? My biggest complaint with the wild ones is they haven't put on much size.

 

I liked the quality of these. Probably Czech Republic ones then at Freßnapf

Czech is very likely. I know other stores here have israeli tankbred.

 

Czech is very likely. I know other stores here have israeli tankbred.

Serious ? Never heard that. Great !

 

In the USA many of the fish farms for tank bred fishes are in florida. There is one specific site that is well known for very hearty cardinals. Our local store finally ordered from them after having large death rates from another seller. They were shocked that something like only 1 out of 350 fishes died.

 

In the USA many of the fish farms for tank bred fishes are in florida. There is one specific site that is well known for very hearty cardinals. Our local store finally ordered from them after having large death rates from another seller. They were shocked that something like only 1 out of 350 fishes died.

Maybe thats where my lfs gets theirs from. They are always super healthy. Very seldom do I see fish with Ich or anything. If there is, there is a huge X on the tank. I've had to wait a few days before too because they just came in and had to QT.

 

Serious ? Never heard that. Great !

Had a chance to look into some wholesaler stocklists when trying to find a female for my Apistogramma.
Two lists said "Roter Neon XL (Israel)". (For the others: Yes, cardinals are basically called "red neons" in German.)

 

I'm surprised that no one mentioned that adding 10 fish to a 10g all at once isn't a good idea.

 

I'm surprised that no one mentioned that adding 10 fish to a 10g all at once isn't a good idea.

Yep if the 10G wasn't cycled I think we have found the cause.

 

I'm surprised that no one mentioned that adding 10 fish to a 10g all at once isn't a good idea.

Oh, as people were talking about the origins of cardinal tetras I thought the case was closed.

 

Wow so many replies! I'm actually from Israel, so is it possible they were actually bred here? Idk... anyway, the parameters I measured yesterday:
Ammonia 0
Nitrites 0
Nitrates ~5-10
Kh ~6
Gh ~6
Ph 6.6
Chlorine 0

Nothing seems out of the ordinary, maybe the ph is still too high? Also I know it's not really valuable info (all the new fish change their behavior when I come to look at them, they all hide from me) but it doesn't really look like the balloon mollies are bullying them... I returned the male to the store so now its just 2 female BMs and the 6 remaining cardinals, and they all look docile...

Anyways, thanks for the help from everyone! Hopefully the rest will make it.

Yep if the 10G wasn't cycled I think we have found the cause.

The tank is cycled, it has been running for about a year and a half now. Unfortunately I don't have a bigger quarantine tank (aquariums are crazy expensive here) which is why I'm using this one.

 

Apologies for not getting that. A 10G should be sufficient to QT these fish.

The only one I can think.of is Ph shock.(a difference between the Ph in the LFS and yours.

 

Actually ph might be too low depending on the source of the cardinals. Most tank bred fishes are raised in their local ph. Recommend parameters like ph,gh,kh are for wild specimens. Most fishes are very adaptable as long as they are gently introduced to the new parameters. There are a few exceptions. I keep my cardinals in local tap which is somewhere between 7 and 7.2 (bloody colour charts). Hum. Amusing the city reports the ph as 7.12 so i guess between 7 and 7.2 is pretty close .
--
Anyway the important thing is nitrite and ammonia is 0 but you did not list temp. If the tank is 62 degree that would certainly cause them cardinals a lot of stress...

Wow so many replies! I'm actually from Israel, so is it possible they were actually bred here? Idk... anyway, the parameters I measured yesterday:
Ammonia 0
Nitrites 0
Nitrates ~5-10
Kh ~6
Gh ~6
Ph 6.6
Chlorine 0

Nothing seems out of the ordinary, maybe the ph is still too high? Also I know it's not really valuable info (all the new fish change their behavior when I come to look at them, they all hide from me) but it doesn't really look like the balloon mollies are bullying them... I returned the male to the store so now its just 2 female BMs and the 6 remaining cardinals, and they all look docile...

Anyways, thanks for the help from everyone! Hopefully the rest will make it.

 

Actually ph might be too low depending on the source of the cardinals. Most tank bred fishes are raised in their local ph. Recommend parameters like ph,gh,kh are for wild specimens. Most fishes are very adaptable as long as they are gently introduced to the new parameters. There are a few exceptions. I keep my cardinals in local tap which is somewhere between 7 and 7.2 (bloody colour charts). Hum. Amusing the city reports the ph as 7.12 so i guess between 7 and 7.2 is pretty close .
--
Anyway the important thing is nitrite and ammonia is 0 but you did not list temp. If the tank is 62 degree that would certainly cause them cardinals a lot of stress...

The temperature is ~80f, it doesn't really change from day to night...

 

Actually ph might be too low depending on the source of the cardinals. Most tank bred fishes are raised in their local ph. Recommend parameters like ph,gh,kh are for wild specimens. Most fishes are very adaptable as long as they are gently introduced to the new parameters. There are a few exceptions. I keep my cardinals in local tap which is somewhere between 7 and 7.2 (bloody colour charts). Hum. Amusing the city reports the ph as 7.12 so i guess between 7 and 7.2 is pretty close .
--
Anyway the important thing is nitrite and ammonia is 0 but you did not list temp. If the tank is 62 degree that would certainly cause them cardinals a lot of stress...

Cardinals are a bit particular. While they can only be bred in extremely soft acidic water, they can live (even wild caughts) in pH up to 7.8 - 8 for quite a while but the changes must be really gentle. So yes, the pH is often the culprit.
62 degrees is like 16°C, right? That should kill almost every cardinal.

 

Gah! Cardinals sound so sensitive to everything... A friend who used to have fish also said he had a lot of troubles with them...

 

I bought 17 cardinals and withing 48 hours I was down to 6. Those 6 are going strong after a year. I am about ready to try to raise the number some tanks been running a year.

 

Wow so many replies! I'm actually from Israel, so is it possible they were actually bred here? Idk... anyway, the parameters I measured yesterday:
Ammonia 0
Nitrites 0
Nitrates ~5-10
Kh ~6
Gh ~6
Ph 6.6
Chlorine 0

Nothing seems out of the ordinary, maybe the ph is still too high? Also I know it's not really valuable info (all the new fish change their behavior when I come to look at them, they all hide from me) but it doesn't really look like the balloon mollies are bullying them... I returned the male to the store so now its just 2 female BMs and the 6 remaining cardinals, and they all look docile...

Anyways, thanks for the help from everyone! Hopefully the rest will make it.


The tank is cycled, it has been running for about a year and a half now. Unfortunately I don't have a bigger quarantine tank (aquariums are crazy expensive here) which is why I'm using this one.

Your water parameters should be quite reasonable for Cardinal Tetras. It is the mollies that won't be happy with the pH. 'Quite often, when obtaining new fish, they might be harboring diseases such as internal parasites that are not immediately apparent. Thus, losses are quite common during the quarantine period and they have adapted to their new homes. Once they have made it through quarantine, they should do well.

 

Of course! But i said that.

62 degrees is like 16°C, right? That should kill almost every cardinal.

 

Your water parameters should be quite reasonable for Cardinal Tetras. It is the mollies that won't be happy with the pH. 'Quite often, when obtaining new fish, they might be harboring diseases such as internal parasites that are not immediately apparent. Thus, losses are quite common during the quarantine period and they have adapted to their new homes. Once they have made it through quarantine, they should do well.

Weirdly, the balloon mollies seem to be perfectly fine... Fish are so weird

 

Thread has been tidied as it had been totally derailed, from the op’s original question.
Please stay on topic & respond to the op’s questions & don’t derail the thread with side discussions