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!

[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...

[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.

[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.

[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.

[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.

[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)?

[bernie]

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

[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(

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

[bernie]

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

[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.

[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...

[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.

[jamesneo]

PH of 7.8 is too high. Tetras prefer acidic water

[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)

[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.

[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

[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.

[gy960]

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

[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.