Would these pH/gH/kH levels be alright for a Cardinal Tetra? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 3 Old 09-16-2012, 12:03 PM Thread Starter
Akeath's Avatar
Would these pH/gH/kH levels be alright for a Cardinal Tetra?

pH: 6.6
kH: 4 degrees
gH: 10 degrees

Are those levels high enough that the Cardinals would be at risk for kidney problems or a shorter lifespan, or are they just at the top of the range for them to live healthily? A lot of profiles have them listed as towards the maximum, but this site's profile has the ideal numbers listed considerably lower. What are the precise levels of pH, general hardness, and carbonate hardness where the calcium blockages in the kidneys and the lower lifespan would become issues?
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post #2 of 3 Old 09-16-2012, 02:12 PM
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It is difficult to pinpoint precise levels of GH and pH at which health issues will absolutely occur. Scientific studies to attain this would have to be very extensive and take into account various factors; not all fish are exactly the same to begin with. By the way, KH is immaterial, as this has no effect on fish or plants, though it does of course serve to buffer pH.

There is also the issue of wild caught fish versus tank raised. The latter have been common in parts of Europe for more than a decade now, and only recently in North America. Observations to date would suggest that tank-raised fish have fewer problems with slightly harder water, though spawning apparently does not occur. But I must emphasize that this is what i have read, and may or may not be complete. So i will confine my remaining comments primarily to wild-caught fish. And, the cited data comes from an article in TFH in 1987 by Rolf Geisler and Sergio Annibal, Ecology of the Cardinal Tetra, Parachierodon axelrodi (Pisces, Characoidea), in the River Basin of the Rio Negro, Brazil, as well as Breeding-related Factors.

Starting with the levels in their habitat, the GH is so low it is basically non-existent. GH of 0.03 dGH was the highest sampled. The pH varied from 3.97 to a maximum of 5.1. More recent samplings by eminent sources such as Heiko Bleher do not vary.

In a study cited in the afore-mentioned article, calcium blockage of the kidney tubes was discerned in wild-caught fish maintained in harder water; upon death the fish were dissected, and it was noted that the longer they managed to survive, the worse were the blockages. No mention is made of the actual GH, but the authors do note that a GH of 4 dGH was successful for maintaining the fish, though they would not spawn in this.

The late Dr. Jacques Gery once wrote that this species will easily live more than 10 years if maintained in very soft water. The fish never lives this long in medium hard water.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #3 of 3 Old 09-16-2012, 09:29 PM Thread Starter
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Well, in that case I'll scratch them off my general tank possibilities list. I don't want to put them in water that isn't within their ideal ranges. Maybe one day if I set up a black water, peat filtered tank I'll get them. Thank you so much, Byron.
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