# Other Aquarium Forums > Fish Care, Nutrition and Water Management >  My Cardinal Tetras are Dying - What's Happening?

## mohgui

i got a 65 litre tank setup up and running for 3 weeks with only substrate and water. i then added plants and left it to run for another week.

during the cycling period... i did checked on the PO, NO3, kH and GH level. but i neglected to check the pH level. the PO and NO3 are almost non-existence. the kH is about 3 and GH is high (more than 10).

i then added around 50 small cardinal tetras into the tank. after 3 days, there will be at least 2 dead everyday. i checked the same water parameters again and i got the same readings. this time, i also checked the pH level and it reads as 7.8.

i asked around and was told that cardinal tetras prefer pH around 5.5... so i got the 'pH Dow' additive. i added and took a reading... it reads as around 6.6. i took another reading the next day... it shot up to 7.8 again.

question is... is the pH level killing off my cardinals? if it's nothing to do with the pH level... then what is causing the deaths? i'm now left with 7 cardinals after introducing them to my tank 2 weeks ago.

btw... my tank is setup as such:

1. CO2 injection (i must say that the CO2 haven't been used for more than 6 months).
2. Eheim eco 130 external filter.
3. a few fist-sized rocks as decoration.
4. some sword type and anubias plants.
5. i don't use stones or crushed corals as substrate. it's those brownish black spherical ones (very small in size).

i really need some help here... thanks!

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## mohgui

i've attached a picture of my tank (the initial days) for reference just in case you guys can spot something which is not right there...

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## lucasjiang

Could be the rocks, some rocks can leach harmful substances into the water. Where did you get the rocks? Secondly, did you measure ammonia levels? Maybe you introduced too many fishes within a short period of time, so it affectedthe water chemistry.

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## PKB

Notice that your plants are swaying to the right and most of your tetra also facing the same direction. Could your outflow to be strong. Just my 2 cents worth of observation.

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## bernie

You should check your ammonia level. Sudden intro of so many fishes will cause ammonia spike, imagine the sudden amount of pee and poo, not enough BB to break them down.
You may encounter bacteria bloom(cloudy water) soon.

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## mohgui

> Notice that your plants are swaying to the right and most of your tetra also facing the same direction. Could your outflow to be strong. Just my 2 cents worth of observation.


i'm also thinking whether the strong water flow will cause stress to the fishes. question... to reduce the water output, i can simply adjust the 'input' and 'output' valves of the filter right? i'm new to this kind of external filter and not sure if this is the way to adjust the water output.

i was on the Eheim hanging filter previously and the water flow can be easily adjusted.

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## mohgui

> Could be the rocks, some rocks can leach harmful substances into the water. Where did you get the rocks? Secondly, did you measure ammonia levels? Maybe you introduced too many fishes within a short period of time, so it affectedthe water chemistry.





> You should check your ammonia level. Sudden intro of so many fishes will cause ammonia spike, imagine the sudden amount of pee and poo, not enough BB to break them down.
> You may encounter bacteria bloom(cloudy water) soon.


i intend to remove the rocks and monitor further. i got the rocks from an aquarium shop in Yishun long time ago. not too sure what kind of rocks are those.

sure... will get the ammonia test kit to test the ammonia level.

btw, pH level around 7.8 should be ok for cardinal tetras (as long as it is stabilized)?

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## bernie

I never check the pH. I just use tap water + anti chlorine. So assume yours should be fine.

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## marcusth

The sudden sway of PH after adding the "PH down" is very dangerous though, just a side note and also if i didnt remember wrongly, i think the ph down is not suitablefor planted tank isnt it??....my current cardinals in my tank was bought in a big packets 35pcs i added all @ once but i slowly acclimatize it just like introducing shrimps by dripping method...

I won exclude the possibility of ammonia spike due to sudden introduction but i feel it could be due to introduction process into the tank or the fact that the fishes you bought were already sick, got check properly when buying??because i had this experience once it were already sick and many died on me within next few days :Sad: ( 

Since you are using a Co2 system, i won worry too much about the PH level, after awhile it will be within 6-7 range which is what my tank PH is. You can probably observe your remaining cardinals first and if everything seems ok after a week or so, add some more in but i strongly recommend dripping methods for all new fishes.

Wish you all the best and await your goods news

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## bernie

About CO2 affecting pH, will too much CO2 cause the water to become acidic and harm the fish?

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## PKB

> i'm also thinking whether the strong water flow will cause stress to the fishes. question... to reduce the water output, i can simply adjust the 'input' and 'output' valves of the filter right? i'm new to this kind of external filter and not sure if this is the way to adjust the water output.
> 
> i was on the Eheim hanging filter previously and the water flow can be easily adjusted.


Yes, you can adjust the valve. Another way is to aim your output against the tank wall.

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## mohgui

> Yes, u can adjust the valve. Another way is to aim your output against the tank wall.


but wouldn't this cause the water to deflect off the wall? i think the fishes are now swimming against the deflected current...

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## PKB

> but wouldn't this cause the water to deflect off the wall? i think the fishes are now swimming against the deflected current...


Yes the current will be deflected off the wall, try deflecting against the back of the tank and observe. The current should be weaken. If the current is to strong, the tank will behave like a washing machine. But again the problem might not be with the outflow afterall, there are many other affecting factors. Observe and check for
improvement for any change you made.

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## jamesneo

PH of 7.8 is too high. Tetras prefer acidic water

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## marcusth

> About CO2 affecting pH, will too much CO2 cause the water to become acidic and harm the fish?



It won change drastically and it takes quite some time before it stabilize @ the range for my case..Just make sure to keep your CO2 within the safety range...just make sure your fishes are not gasping for air on the water surface....aerate the water when light off will helps alot, dispersing CO2 and boost oxygen level in tank... 

Do regular water change and remember to use aged water(24hrs prepard beforehand)  :Smile:

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## mohgui

thanks for all the replies... will take into consideration all tips and see how things go... i'm down to 5 tetras now... sad.

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## gy960

IMO, using chemicals to alter water chemistry is risky. The ph down solution is phosphoric acid (it it?) and can lead to unwanted algae grow. (?). Ever consider filtering over peat? Nice set-up btw  :Smile:

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## mohgui

> IMO, using chemicals to alter water chemistry is risky. The ph down solution is phosphoric acid (it it?) and can lead to unwanted algae grow. (?). Ever consider filtering over peat? Nice set-up btw


yes... am considering peat. but not sure if the water will turned brownish over time.

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## gy960

Yup, peat will make the water brownish 'cos there is tannin acid, thats why ph turn acidic.

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## bernie

Where did you get your cardinals from? Every suspect are the fishes that have the problem? Are they from a tank of water that wasn't colourless? Probably they were undergoing some treatment when you bought them.

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## gy960

But if the cardinal tetras are breed in Singapore farms, not sure if they are reared in normal Singapore tap water (base pH). Then the tetras are used to neutral/alkaline waters.  :Smile:

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## o2bubble

Likely due to ammonia spikes and maybe sudden ph change. Did you let your tank cycle for at least 3 weeks before you add cardinals and you should add slowly e.g. 5-10 at a time and each time let the fishes adjusts to the water temperature first before releasing from the bag? Also, when you change water did you add anti chlorine like seachem prime which neutralizes chlorine and does not produces ammonia based side products? Also, cardinal can adjust to waters from 5 to 8 ph levels, so no need to lower ph although they show best colors around ph 6-6.5. Try to remove ammonia and add some beneficial bateria solutions to improve your waters. Do not keep changing water and let your tank cycle properly first (change <50% once a week is enough). Just my 2-cents worth based on similar experience. Lastly, hopefully some of your cardinals survives at the end. Hope it helps.

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## mohgui

> Where did you get your cardinals from? Every suspect are the fishes that have the problem? Are they from a tank of water that wasn't colourless? Probably they were undergoing some treatment when you bought them.


got them from Sea View Aquarium at Seletar West Farmway 2. i got 50 at one go because it's cheaper in bulk. and the guy got the fishes from the inside and not from the display tank. so i'm not sure what colour was the water from the inside tank.

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## mohgui

> But if the cardinal tetras are breed in Singapore farms, not sure if they are reared in normal Singapore tap water (base pH). Then the tetras are used to neutral/alkaline waters.


that's what i thought so too... unless the breeding farms conditioned their water. i think i must start to use additives to remove minerals from the tap water.

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## mohgui

> Likely due to ammonia spikes and maybe sudden ph change. Did you let your tank cycle for at least 3 weeks before you add cardinals and you should add slowly e.g. 5-10 at a time and each time let the fishes adjusts to the water temperature first before releasing from the bag? Also, when you change water did you add anti chlorine like seachem prime which neutralizes chlorine and does not produces ammonia based side products? Also, cardinal can adjust to waters from 5 to 8 ph levels, so no need to lower ph although they show best colors around ph 6-6.5. Try to remove ammonia and add some beneficial bateria solutions to improve your waters. Do not keep changing water and let your tank cycle properly first (change <50% once a week is enough). Just my 2-cents worth based on similar experience. Lastly, hopefully some of your cardinals survives at the end. Hope it helps.


yes... tank cycled for 3 weeks before introduction of fauna. maybe as what most of you guys mentioned, there could be a spike in ammonia. i have yet to get the test kit to confirm this though.

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## bernie

Consider getting XL size of cardinal tetras, there are more resilient.

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## mohgui

ok... i've done some test to the water and here are the results:

Nitrate - 0.00 ppm
Phosphate - 0.5 ppm
Ammonia - 1 mg/l
pH - 6.8

i've got 4 tetras left and these 4 lasted for a few days already. i guess they adapted to the water condition.

i also added peat granules to the filter. hopefully, it will lower the pH and get it stabilized before i add more tetras.

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## gy960

Ever considered the hardier glowlight tetra?

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## mohgui

> Ever considered the hardier glowlight tetra?


i prefer cardinal tetra because of the brilliance of the red and blue against a green background (plants).

btw, how much is the glowlight tetra?

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## gy960

Usually same priced as cardinals or neons. +/- $1 at qianhu.

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## itxno1

Too much would affect the PH and harmful to fish also. It makes the fish hypoxia.
Secondly, too many fish introduced into your tank at once may cause ammonia shoot up to toxic level that cause fish die.

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## Dean

I totally agree that introducing fish at that amount can cause ammonia spike especially when the BB couldn't cope with so much bioload at that time. I recommend adding 6~10 fish at a time and introduce the second batch 2 weeks later. Cardinal tetra prefer acidic water too. I hope you have better luck in keeping them now.  :Smile:

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## Merduka

Hi bros,

Saw this thread and could not resist as well. I hv almost a similar set up... ther bro can kindly confirm the substrate used? I was recommended the light brown pellets (small balls) from Colorful West Coast. This is my 3rd time recycling my 2ft tank - all my tetras died as my 2nd hand eheim started spewing white foam. Fixed that with KY jelly. 

My quesru, I noticed the outlet Eheim is submerged? Is this the correct way as mine is above spewing like the Merlion.

Regards
Merduka

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## bernie

Are you dosing fertilizer , flourish excel ? I think cardinal tetra are very sensitive.

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## mohgui

> My quesru, I noticed the outlet Eheim is submerged? Is this the correct way as mine is above spewing like the Merlion.


i submerged the outlet because i feed CO2 through it. i'm using the water flow to spread the CO2 distribution.

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## mohgui

an update to my tank; i recently added 11 cardinal tetras (larger in size) to my surviving 4. it's been 4 days already and none died yet. looks like my tank has stabilized. i've also introduced peat into the filter. but the pH level is still hovering around 7. i would like to bring it down further, but if the fishes are happy about it... then i should too  :Wink:

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## wcneo

what soil u brought? some soil have high ph. if the soil ph is those high one, u try what also no use as it will keep push back to it normal ph lvl.
check the soil packing or ask the shop owner. current might be to big but the eheim you have can be tune to slower flowrate.

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## chilla18

I suspect that SeaView cardinal are not properly condition I brought 100 pcs and within 1 month left with less than 20 fish everyday 2-3 cardinal will die.

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## wcneo

when u buy did u see the water colour in the bag? if got colour mean the fish not too good so they add chemical in. u can try at c328 there cheap and good. i last time buy only 1 to 3 die till i change into shrimps tank

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## chilla18

No colour in the water that comes with the bag. Any idea how much is C328 selling for the cardinal as it has been some time since I last visited them.

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## wcneo

if i remember correctly is should be 50 for $30. i think not too sure as i now go for shrimps not cardinal anymore.

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## chilla18

Wow if 50 for $35 that that is a huge difference Seaview is $35 for 100 that could be the reason why Seaview is selling so cheap, most likly the fish are not properly condition.

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## wcneo

i not too sure maybe is 100 for 30 or 35 like that ba. coz mostly i but is neon tetra. 50 for 6dollar

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## lizhien

I've had a similiar experience too. I had >70 cardinals, all bought from seaview. 90% died within a week. I guess i introduced too many fishes into the tank at 1 shot and the BB couldn't cope. =( my current batch of tetras are doing better. have less than 20% loss so far. Its been 2 mths since i've introduced them into the tank.

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## chilla18

I have brought another batch of 100 cardinal from SeaView about 2 weeks ago so far so good and I'm monitoring it let's cross our finger. Lizhien is your current batch also brought fro SeaView?

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## lizhien

Yup.. Consolidated all the tetras into a larger 2ft tank with more live plants. I think they will be happier there. My previous set up was to have <20 tetras in my 1ft tank to keep the bioload down, but i think the lack of large 'shady' plants have affected them. They sort of lost their 'hiding plance'. I'm considering adding more tetras into the communal tank. Any idea if the 2 ft tank can support >100 tetras?

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## mohgui

i wouldn't want to attempt putting >100 tetras in a 2ft tank. wouldn't it be too cramp for them to be moving around?

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## mozesyap

100 in a 2ft? Are they still alive?!
I only have 100 in my 6 feet... and I think it is only just nice..

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## stmoo

not advisable to put 100 in a 2ft, my 4ft only have 100 pcs. 
would recommend 20-30 will do for 2ft, at least they have more area space to swim around.

as for the Cardinal Dying may the the cause of NTD http://freshaquarium.about.com/cs/di...eondisease.htm
i got this once before and every day 2-3 tetra dying.

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## mohgui

> not advisable to put 100 in a 2ft, my 4ft only have 100 pcs. 
> would recommend 20-30 will do for 2ft, at least they have more area space to swim around.
> 
> as for the Cardinal Dying may the the cause of NTD http://freshaquarium.about.com/cs/di...eondisease.htm
> i got this once before and every day 2-3 tetra dying.


yah... same observation when my cardinals started to die... every day, about 2-3 will die.

but the article mentioned that cardinals are kind of immune to NTD... *Interestingly enough, Cardinal tetras are resistant to the ravages of Neon Tetra disease.*

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## stmoo

the batch of Cardinals i kept for around a year and they just got this NTD. 100pcs were totally wipe out within 2weeks.

so from then on, i don't dare to keep Cardinal for years, i change to rasbora. until this year i bought small size 100pcs from sea view, so far so go, now they are big Big size  :Razz:

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## chilla18

But cardinal very swee to me so I still prefer Cardinal till date my 100 cardinal from sea view is doing fine.

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## IAMTHOMAS

Looks over crowded, Perhaps you introduced the fish way to fast and your filter couldnt handle the bioload?

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