# Cardinal tetras dying in established tank



## All that is Fishy

Hi everyone! 

This is my first post here. I am posting because some of my cardinal tetras have been dying and I can't figure out why. I was hoping someone could help me.

About my tank:
-I have a 38 gallon tank that has been running for 11 months. 
-I keep the temperature at as close to 80 degrees as possible, though it sometimes goes down to 79 or 78, in which case I adjust the temperature. 
-I do 40% water changes once per month, because I had heard and read that that was okay. Then I heard it should be every week (just recently), so I am now going to change it every week, but probably just 30%. 
-I usually don't check the parameters of the water now, because they had been stable for a long time. I just checked it, though (before my water change on Monday), and the levels of ammonia, nitrates, and nitrites were fine. There is no visible algae, and I clean the inside walls of the tank when I change the water. 
-My pH is, and always has been, high (I think about 8, maybe a little less)

The fish I have:
-1 small pleco (about 2 inches, though he will grow to be 5-6 inches)
-1 pictus catfish (about 4 inches, though he may grow another 2 inches or so)
-1 guppy
-2 platties 
-2 dwarf gouramis 
-1 blue ram
-4 cardinal tetras (sadly... there were 7)
-And, the new guys: 3 (what I think are) blue emperor tetras 


Probably about 3 weeks ago, I added 3 blue emperor tetras, and all but one died. Since I have had trouble with cardinal tetras when I first added them months ago, I thought they may not have transitioned well. So, I bought 5 more, plus 2 more cardinal tetras. (The lady at the fish store said it would be fine because tetras produce a low bio-load). Anyway, the next week, a cardinal tetra was missing, and I thought it was because I went away for a few days and the temperature dropped to 76 (my fiance was watching them, and I didn't give her careful enough instructions on how much to adjust the temperature if it deviated from 80). Then, the next week (this week), there are only 4 cardinal tetras and 3 blue emperor tetras left (plus the other fish)! I have no idea what is going on, because I had the same group of 7 cardinal tetras for months and they were fine. Now they are dying. 

What could be happening, and how can I fix it? 

Thank you!!


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## Arbiter120

All that is Fishy said:


> Hi everyone!
> 
> This is my first post here. I am posting because some of my cardinal tetras have been dying and I can't figure out why. I was hoping someone could help me.
> 
> About my tank:
> -I have a 38 gallon tank that has been running for 11 months.
> -I keep the temperature at as close to 80 degrees as possible, though it sometimes goes down to 79 or 78, in which case I adjust the temperature.
> -I do 40% water changes once per month, because I had heard and read that that was okay. Then I heard it should be every week (just recently), so I am now going to change it every week, but probably just 30%.
> -I usually don't check the parameters of the water now, because they had been stable for a long time. I just checked it, though (before my water change on Monday), and the levels of ammonia, nitrates, and nitrites were fine. There is no visible algae, and I clean the inside walls of the tank when I change the water.
> -My pH is, and always has been, high (I think about 8, maybe a little less)
> 
> The fish I have:
> -1 small pleco (about 2 inches, though he will grow to be 5-6 inches)
> -1 pictus catfish (about 4 inches, though he may grow another 2 inches or so)
> -1 guppy
> -2 platties
> -2 dwarf gouramis
> -1 blue ram
> -4 cardinal tetras (sadly... there were 7)
> -And, the new guys: 3 (what I think are) blue emperor tetras
> 
> 
> Probably about 3 weeks ago, I added 3 blue emperor tetras, and all but one died. Since I have had trouble with cardinal tetras when I first added them months ago, I thought they may not have transitioned well. So, I bought 5 more, plus 2 more cardinal tetras. (The lady at the fish store said it would be fine because tetras produce a low bio-load). Anyway, the next week, a cardinal tetra was missing, and I thought it was because I went away for a few days and the temperature dropped to 76 (my fiance was watching them, and I didn't give her careful enough instructions on how much to adjust the temperature if it deviated from 80). Then, the next week (this week), there are only 4 cardinal tetras and 3 blue emperor tetras left (plus the other fish)! I have no idea what is going on, because I had the same group of 7 cardinal tetras for months and they were fine. Now they are dying.
> 
> What could be happening, and how can I fix it?
> 
> Thank you!!


Hello there, welcome to the forums!

It seems as if you are adding too many fish at one time. The general rule is to slowly add 1-3 fish in one week only. Adding over 4 fish in the same week will cause a bio-load buildup and will cause the ammonia to spike. The fish you are adding could also be stressed due to the bio-load buildup when they are being added to your aquarium.
Whenever I add my fish, I usually float them in their bag in the tank for 10-15 minutes, then I add 20% aquarium water to the bag. I wait for around 15 more minutes, then net them into the tank. When fish become stressed, their slime coat that protects them from disease, weakens. This makes them more prone to diseases. Do they show any symptoms of disease when they die?


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## Byron

You don't mention finding the dead fish but just they are going missing. Is this the case? Are the fish dying and you are taking out the dead corpse, or are they just disappearing?

I ask because the pictus catfish is a known predator and being nocturnal and at 4 inches it may well swallow small fish at night. There are some other issues with the mix of fish, but I won't go into all that just yet. Let's deal with the fish losses first.

And another thought on that, you mention the pH at 8 which is certainly high for cardinals and Blue Emperors too, but more important is the GH (general hardness). What is the GH of your tap water? You can find this out from the municipal water supply, they likely have a website. GH is of more importance to fish than pH.

Byron.


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## All that is Fishy

Hi! Thank you for your replies! I would have come back to the forum sooner, but for some reason I thought that if I got a reply, I would get an email. I am glad I decided to come back and check. 

My GH is about 300. I didn't ask the water company, but I have a test kit, and the color indicated that it might have been a tiny bit under 300, but I think 300 is a good estimate. 

The fish bodies ARE disappearing, so I don't know if they show any signs of disease once they're dead (though they don't when they are alive the night before they go missing). When some had gone missing in the past, I checked the filter, and I could not find them. I thought someone (a fish) might have been eating the dead bodies. Only one time did I find a body. I would not be surprised if my catfish was eating them at night, because he is significantly bigger than the cardinals. 

Also, the people at the fish store said, "If you're putting in fish as a school, put them all in together," and, about the tetras, "They are so small it won't really affect your bio-load." Maybe that was bad advice! I started thinking that maybe the tank is just stable with 7 tetras... That is what I had before, and after adding fish and fish deaths, I ended up back at 7. Luckily, no more have died since I last posted. 

As for the balance of the fish, when I started my aquarium, I made a list of fish and their water parameter requirements. Some were a little different, but a person at a different fish store said it was close enough. I have specifically asked, "Here is what we have. Is this a good fish to add?" And they have said it was fine. What I am thinking is that--given both of your feedback--maybe a fish store is not the best place to get advice, since they want to sell fish. Still, I thought the last store I found was really good. 

I feel like I am coming across as a fish owner who has not done her research, but I actually have. I am so enthusiastic about fish and aquariums. I hope to get some suggestions that will help me improve my fish keeping skills. 

Thank you both!


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## All that is Fishy

I just looked at the pictus catfish profile page on this site. I am completely serious that the person at the store said he was peaceful and would NOT eat smaller fish. 

I am not really sure about what to do about my catfish. Everything has been in balance except for when I added tetras to over 7, so maybe things will be fine. But, he is just alone, and the page I looked at just now said they need to be kept in groups of 5 or more, and in only 55 gallon tanks or more. Mine is only 38 gallons and I have no more room for fish in the tank. He does have a nice hiding spot that he likes under a piece of aquatic wood, so I think that is good. Any other suggestions? (and, by the way, what I would LOVE to do is getting a bigger tank, but my fiance has vetoed that idea a bunch of times, though eventually, when we get a bigger house together, we will get a 200-gallon one. So, I don't think a bigger tank is something that I can do in the near future.) 

Also, I have tried to lower the pH before when I first got the tank, but then people told me (and I read online) that lowering the pH is generally not a good idea because it makes the tank less stable. Or at least with chemicals. I don't want the yellow-y water look that I have heard accompanies peat moss. I have aquatic plants and some driftwood. Is there anything else I should do? Is that even something to worry about?


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## Byron

Lots of issues/questions in your two posts, so I'll try to answer everything.

Fish stores can be good or bad when it comes to the knowledge of staff. I have been in both. I was very fortunate that when I got started seriously in this hobby, I was dealing with a very good store owned by hobbyists and fully staffed by hobbyists. Looking back, I realize just how valuable that was. When I moved to Vancouver and got back in the hobby with even larger tanks, I was again lucky to have such a store that I dealt with. I have often been in other stores to browse and some of the advice I overhear makes me cringe.

To your pictus. All things considered, I would see if the store will accept it back, perhaps in a trade for other fish. I know some aquarists have a lone fish and it seems to be fine; it likely is not. Fish that have evolved to live in groups do so for a reason, and there is now scientific evidence that being denied this does affect the fish's homeostasis and causes stress, and stress is the direct cause of 95% of all fish disease. So this has serious ramifications. Plus, it will continue to grow and eat smaller fish. I've not much doubt that this is where your cardinals went.

To the water parameters. On these too there are varying opinions, but as the scientific evidence rises, fewer and fewer can deny the significance on fish. I agree one has to be careful in adjusting these, as there are safe methods and unsafe methods, and fluctuating parameters are worse on fish. GH at 300 (presumably ppm) is around 17 dGH, and that is fairly hard water. Cardinals will not find this easy. The lifespan of cardinals (and many other soft water fish) is proportionally related to the GH; the higher the GH, the shorter the lifespan. The calcium which is the prime mineral affecting GH builds up in the fish and clogs the kidneys; this cannot be seen without dissection. The more calcium, the faster, until the fish just dies. My little article on GH and pH may give you some background:
http://www.tropicalfishkeeping.com/...water-hardness-ph-freshwater-aquarium-188705/

On adding all fish in a group (shoaling or schooling species), I fully agree. That is always wiser, for two reasons. Some species establish a social pecking order within the group, and adding fish later can cause trouble by upsetting this structure. It is better to acquire such fish all at once. This does not mean that you cannot add more later, it depends upon the species. The other reason which applies to all shoaling species is that there is safety in numbers, and fish stress will always be lessened the more fish there are in the group. A larger group will settle down in a new environment much faster than a couple fish. For more reading;-) my article on stress:
http://www.tropicalfishkeeping.com/...icles/stress-freshwater-aquarium-fish-188673/

Byron.


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