Cardinal Tetra Mortality

[dasaltemelosguy]

Hello, I'm not sure this is the correct category to post this but perhaps someone with experience with Cardinal Tetras may know what might be going on here. It is a 75G and has a SunSun704b canister and the output was modified to distribute the spray across the entire length to reduce the current so they could eat on top or in the column. I try to over filter my tanks and accommodate these tiny fishes.

I have a 75G planted tank that has been cycled for months as I've used it for grow out of juvenile cichlids until they're large enough to join a larger tank. The parameters below have been extremely consistent for many months:

• pH = 7.8
• Nitrates = 5ppm
• Hardness = 140
• Nitrite = 0
• Ammonia = 0
• KH/Buffer = 70
• Water Temperature = 80*

One day prior to this population below, it housed 12 adult Blue Acaras, two juvenile plecos and a juvenile algae eater. The Acaras were moved to a 120 and the following day, the juveniles below arrived.
In this tank now (for about 2 weeks so far), I have 12 juvenile Silver Dollars (about 3/4" in size) and 50 circa 3/4" Cardinal Tetras. The Dollars love it. Actively swimming end to end in schools and no visible shyness. The Cardinals look robust and school as well as explore the tank and as far as I can tell, all of them eat well. The little algae eater and small plecos are active and eat well too (obviously they're in here for grow-out) .
Every day since getting the Cardinals, I lose about 2-3 of them/day. I don't sense any stress or obvious illness and I see nothing externally on them. I find a dead ones in seemingly perfect condition lying on the gravel throughout the day which naturally I remove. Each day I find more bodies. No evidence of trauma, I'd have to pick them up and verify they're dead.
After two weeks, there's perhaps 1/2 of them left.
I have never kept Cardinals before. They currently share this 75G with two juvenile plecos and a small algae eater (also in grow-out) and the aforementioned juveniles, 12 Silver Dollars. NONE of the others exhibit any sign of distress nor illness. Very active, eating and already some visible growth. And the surviving Cardinals eat voraciously yet ONLY the Cardinals seem to be slowly dying.
When I bought the school of 60, I assumed there would be some mortality with that many but there's now less than half of them left after only 2 weeks.
I did ask the shop where I got them and they said "they were acclimated to a 7.4PH environment". When they arrived, the PH in the bag was only 6 so I set up a drip overnight and introduced them into my tank at 7.8PH at which point, they matched.
At that point, I had only 9 die and the other 50 were looking excellent.
I have no experience with these fishes. I've only kept large cichlids and this is my first foray into schooling fishes. And I should note it is planted but not heavily. I'm not confident there are enough hiding places for the Cardinals.
I see a great deal of discussion about PH for Cardinals but I was wondering if others had ideas on how truly significant that is. With most fishes, if properly acclimated, they'll adapt to most any PH.
But again, I've never had Cardinals. My other tanks have Severums, Acaras, Oscars, Pacu's, Plecos, all grown from <=1" to +14" in some cases over 2+ years with very few incidents. I've never had an entire species just start dying with no apparent (to me) cause.
Does anyone out there have any thoughts on what I might be doing/have done wrongly that is killing off the Cardinals and if it's possible to save the rest? Thanks so much everyone.

 

[seangee]

When my local shop acclimates fish they mean they chuck them into water and anything that doesn't die within a week is called acclimated. Unfortunately that is not the way it works.
I have kept cardinals for many years and the mortality is very low with a typical lifespan of 5-6 years. My water parameters are similar to their natural environment
pH = 6
GH = 0
KH = 0
Temp = 25C

They do not do well in hard water but if that were the issue I would expect them to start dying after a year or so and not immediately. Your hardness numbers (assuming you mean ppm or mg/l) are not ideal but also not terrible, so I can't really account for your problems unless they arrived with a disease or infection.

Just FWIW cardinals "school" when they are stressed. They typically hang out in small groups but do not school.
They also do not like a lot of light, fry and eggs cannot tolerate bright light and will die. Floating plants are also recommended. They naturally occur in forests and do not know that your room does not have birds waiting to pounce on them. When I have part of the surface coverered they invariably stay in the covered area and avoid the "clear" water areas.

 

[Avel1896]

Hi
No matter what LPS/LFS claim, Paracheirodon "cardinal tetra" axelrodi is a soft acidic and black water fish.
• Ph should be 6 or below.
• Hardness should be 6°GH maximum.
• Alcalinity should be 4°KH maximum.
If you want to save the rest of Cardinalis, give them a densely planted and dimly lit aquarium providing parameters given above.
Good luck

Paracheirodon axelrodi – Cardinal Tetra (Cheirodon axelrodi, Hyphessobrycon cardinalis) — Seriously Fish

www.seriouslyfish.com

 

[dasaltemelosguy]

I can certainly give them more hiding places and more plants and reduce their stress. The PH I can lower over time and hope enough survive. Thank you everyone.

 

[dasaltemelosguy]

When my local shop acclimates fish they mean they chuck them into water and anything that doesn't die within a week is called acclimated. Unfortunately that is not the way it works.
I have kept cardinals for many years and the mortality is very low with a typical lifespan of 5-6 years. My water parameters are similar to their natural environment
pH = 6
GH = 0
KH = 0
Temp = 25C

They do not do well in hard water but if that were the issue I would expect them to start dying after a year or so and not immediately. Your hardness numbers (assuming you mean ppm or mg/l) are not ideal but also not terrible, so I can't really account for your problems unless they arrived with a disease or infection.

"Just FWIW cardinals "school" when they are stressed. They typically hang out in small groups but do not school. They also do not like a lot of light, fry and eggs cannot tolerate bright light and will die. Floating plants are also recommended. They naturally occur in forests and do not know that your room does not have birds waiting to pounce on them. When I have part of the surface coverered they invariably stay in the covered area and avoid the "clear" water areas."

I have a sense you are correct. They do huddle as 1 or 2 groups largely which supports your observations. It's also something I can try immediately whereas the PH reduction will have to take much more time for safety. But i will try both. Thank you.

 

[Myraan]

This is strange. The gH and kH are relatively low. Is the highish pH which maybe the cardinals do not like the pH of you tap water or the pH your tank seems to stabilise at? My neons died off gradually over the course of a year or two, but everyone seems to reckon they are really delicate compared to cardinals (20 yrs ago the received wisdom was the opposite). I gradually replaced their shoal with cardinals, that other than the odd unexplained death/disappearance look healthy and happy, the oldest ones being 3 yrs old or maybe more.

My first thought is maybe you did more harm than good with the overnight drip acclimation. I have much less experience with fish than most on here though; my experience is too much of this forum reading other peoples problems for years before buying my tank. I'm guessing the bag or bags of cardinals were chock a block full of ammonia and carbon dioxide just from the fish being in them on the journey home. The carbon dioxide would have lowered the pH to the point that the ammonia was in the form of ammonium and much less toxic. When you slowly acclimated them, indeed when you opened the bag and exposed it to the air, the pH would have risen, making the ammonia toxic. Being acclimated over night meant the ammonia was poisoning them for several hours at least. This is where my knowledge breaks down due to lack of experience. I have read that ammonia damage to gills is irreversible; could this cause them to be weaker? Could the silver dollars be stressing them? My neons I had at the start used to be scared stiff of the dwarf gourami I used to have, yet the loved the company of a very bossy Ram. Maybe its a pheremone thing.

I used to follow the instructions on the fish bag to acclimate to water chemistry, but I since learned that any getting used to chemistry in physiological terms either will not happen due to basic biology or will take weeks. So now I just float them to acclimate temperature then tip them into a net over a jug to get em into clean aquarium water as soon as possible after bag has been opened.

 

[Colin_T]

Pictures and video of the fish?

If the fish had only just come into the shop, they would be stressed from the move. Then by putting them in a tank with a much higher pH, that added to the stress. If you have to buy fish, get them a week or two after they have come into the shop, and buy them the day before the shop does a water change. Also try to get the pH closer to whatever the shop has so there is less difference.

The combination is probably a contributing factor to them dying. However, without seeing pictures and video I can't be 100% certain they don't have a disease, which is causing the problem.

 

[dasaltemelosguy]

I suspect you're both correct. I bought them online and paid for overnight shipping to reduce stress as they normally ship by USPS which can take 3 days (so much for that idea!). As you said, the CO2 no doubt dropped the PH in the bag to <6 so I didn't know which was the lesser evil, releasing them into a clean but much higher PH tank or an overnight acclimation. As you pointed out, as a precaution I pre-treated their water with Prime, assuming ammonia would build and put a layer of zeolite on the bottom of their bucket as well. The following day, there were 9 fatalities but the rest (about 50) looked energetic and colorful. They eat voluminously and swim the entire tank but only as a school (stressed?) and each day, there's dead bodies seemingly perfect in appearance lying on the gravel. The Dollars are juveniles and at present, not much larger than the Cardinals and seem to totally ignore them.

I've literally watched the Cardinals eat, eagerly and with energy, and suddenly drop to the gravel dead minutes later. So perfect in appearance, you have to pick them up to know they've perished.

They just seem to swim, eat, and suddenly drop down and die. Just a few a day, and often right after they eat. There's really no visual evidence of illness. Not a spot nor any swimming distress I can see. Full of color and full of energy, nice round bellies, and yet they just drop.

I suspect you're all correct and I hurt them during the acclimation. Thank you again everyone.

 

[Myraan]

I wonder if a fish shop buying same amt see similar deaths - and when we the customer buy the odd 4 we are getting the strong ones - that is unless i was right the first time round anyway

 

[itiwhetu]

Cardinals and Silver Dollars are at opposite ends of the tetra spectrum and are not good tank mates. The Dollars will just scare the wits out of the cardinals.

 

[Colin_T]

post pictures so we can check them for disease

have you contacted the seller and informed them of the deaths?

If they are dying straight after feeding, reduce feeding for a week or two and don't do any water changes unless you get an ammonia or nitrite reading. See if they settle down.

Put some floating plants in the tank or reduce the lighting. Maybe even turn the light off for a week and that can help reduce the stress on the fish and might help.

 

[dasaltemelosguy]

I will definitely try that. I did speak with the dealer and they said a PH up to 8 would be fine as they keep them at 7.4 but recommended a 1 hour acclimation with 15 minute introductions of tank water to their 'bucket'. When I saw a PH of under 6, I perhaps wrongly, elected for an overnight drip.

I would imagine this suggests they are tank bred but of this I am still uncertain. My guess being they try to keep them acclimated to a PH they're more likely to face once sold to the general public. But I am just guessing, they did not say this. They added 20 additional fishes so given most of them probably end up in less than ideal conditions or with neophytes, the mortality must be fairly high. They are primarily a Discus dealer although they carry fishes they consider suitable tankmates for Discus.

At least at this stage, stress seems to be a major if not the primary component. I'll shoot some images and post them as well should you see something I'm not seeing. Thanks so much for your help.

 

[itiwhetu]

Cardinals will only breed in very soft low pH tanks. I very much doubt that any Cardinals are tank raised for commercial sale. The fact that this guy breeds Discus implies all his systems will be soft and acid.

 

[Byron]

@dasaltemelosguy, the drip acclimation could have been the issue here. The pH of 6 for the bag water means that any ammonia would be primarily ammonium which is basically harmless. However, as soon as you began adding water with a 7.6 pH, if the pH in the bag did rise above 7 then the ammonium changes to toxic ammonia. This is one big problem with any form of mixing water "acclimation."

The second point is that fish cannot adapt to a significant pH or GH variation in hours, nor even days; it takes weeks because of the physiology of the fish. Which is why so many do not recommend any form of acclimation other than equalizing the temperature. Not everyone thinks this is needed either, but it is true that a temperature change that is sudden and more than several degrees can be fatal. So I still float the bag until temperatures are the same to my hand.

I'm only pointing out the issue, without advocating it is "the" issue. But the stress of any significant change would certainly add up whatever the actual issue causing death. And fish that have lived through an ammonia issue can frequently appear OK but drop dead in a matter of days., sometimes longer, because of the impact to their physiology.

 

[Colin_T]

I very much doubt that any Cardinals are tank raised for commercial sale.

Cardinal tetras have been bred in Asia for years. A few shops sell wild caught fish but they will be labelled "Wild Caught" and cost more than captive bred specimens.