Tips for Cardinal Tetras

jesusjones

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I have been keeping cardinal tetras for maybe 4 years now and think I have finally figured at least one thing that may help out some others. My Cardinals have always been very skittish and sorta seemed stressed. They would eat, but sometimes lose there appetite for a day or two and they would always be hiding and schooling in the back, riding the glass and all sorts of stressed looking activities.

Adding wood decor and plants that extend from the substrate all the way to the surface seems to create an environment where they feel safer. They like to hide and relax in the shadows but also like to be able to see out into the open. I had black substrate (Flourite) originally that I changed out to sand for them also. The sand is less sharp and more natural to them. They will poke about in the sand but always seemed to be weary of the black sharp substrate.

But even with all this my fish always seemed to be on very high alert, like they could sense something. So, eventually, I'm poking around my tank with a voltmeter and I measure some voltage in the water of the tank (this is referred to as stray voltage by some and not well understood by most). The canister filter inside my tank had some leakage, in fact all my tanks with an impeller pump measure some voltage! But most fish don't seem to care or notice. That is where I think Cardinal tetras differ though, Cardinals come from soft, non-conductive, water and therefor probably have a higher ability to sense electrical signals in the water than other species (fish have electrical sensory organs). They need to be more sensitive to it because the signals are normally so weak in the soft water they naturally come from. Now, put them into a tank with much harder, conductive, water and the electrical signals from anything will be overpowering for their senses (I figure). So I took out the impeller pump and added sponge filters running on air. They calmed right down, still skittish fish for sure, but they always have an appetite, never glass surf and just seem happier.

So I recommend, for keeping cardinals, to not have any impeller pumps that may cause electrical noise/signals in the water. I'll see if I can get a photo up later to share.
 

GaryE

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Interesting. Just speculating, but I know some of their predators locate prey by sending out weak electrical pulses.

I find shading from above, heavy planting and wood up towards the surface overhanging makes them be very out and about. Bareness is death when you're that size

I'm into my 3rd major group of cardinals. i bought 50 and got 7 years out of them, then got 100, and had to move them out after 5 years, when I moved. I just restarted a bunch of wild caughts, and they are very outgoing, within limits. I use a canister and 2 HOBs on their 75 gallon/280 liter tank.
 
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jesusjones

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It was a lot like they thought a predator was lurking around the corner all the time. I have had around 25, but struggled to keep them thriving. They would do OK, but seemed stressed as mentioned. One by one, over time, they would get ill, white tumor growths at the tail base, bloat or getting very skinny. I thought maybe my tank was infected with something. With the fish now showing less signs of stress these random illness issues have also stopped.

I'll add that having more than enough filtration for them is probably more important than worrying about impeller pumps and "stray voltage". It is possible that the canister filter I used might of been undersized for the bioload and caused my issues. It was 70GPh with a fist sized block of foam inside, tank is ~25 G with only 15 cardinals max. Now, using 2 fist sized bubble filters, things seem better. But unplugging that canister did always seemed to have a calming effect.....

I chased this "issue" for a while, hope some of this helps someone figure out their skittish fish :)
 

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jesusjones

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I wonder if it was enough current to trip a GFI
Good question and reminds me of a relevant story. I just now went to test it out in a bucket, plugged the filter into a gfi outlet and ran a ground from the same outlet into the bucket. It did not trip, it ran in the bucket for a few minutes while I checked some things.

With the bucket of of water grounded you can not measure any voltage between the water and ground (normal). When you disconnect the bucket ground there is a reading of 30 VAC in the water (odd, but seems normal from the pumps I've tested). The voltage increases slightly when you measure closer to the pump/power cord (pump is the source). Does it actually leak enough to be a hazard or matter?...the GFI outlet didn't seem to think so.

The story and another reason I suspected the pump. One time, the tank was on a basement concrete floor and I was barefoot (with water everywhere probably), sticking my hand into the tank I was clearly feeling a some mild tingling of an electrical shock, like acidic water on rough hands. I was more careful to wear shoes after that but didn't think much of it at that moment.
 

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