Nephrocalcinosis - are we being cruel to our fish?

[ajm83]

Read this today:

http://www.practicalfishkeeping.co.uk/content.php?sid=6769

The claim being that adding high levels (>12ppm) of co2 to the water can cause problems for the fish.

Less contentious, and my greatest worry for long term CO2 use is a condition known as nephrocalcinosis. This one is well recorded as a problem within aquaculture, and has been known to rear its head in Danio rerio circles too. The relationship between the condition and CO2 isn't entirely clear, but is thought to be related to fish compensating for blood acidosis, resulting in the excretion of calcium and phosphorus.


Calcinosis as a general ailment involves calcium deposits in the flesh of a fish, while nephrocalcinosis involves calcium deposits within the kidneys. Typically it is found in fish kept in high concentrations where CO2 reaches >12ppm, and more frequently in alkaline conditions. However, it doesn't only occur in alkaline conditions, and in some cases it appears that CO2 concentration alone is enough to prompt it. Given that the average gas-fuelled aquascape will be riding at a level in excess of 12ppm, it's not too hard to see the potential for a link.

Anybody know any more about this? I have not had any unexplained deaths in my pressurised tanks, but am not particularly comfortable keeping fish in conditions which cause them discomfort.


(With apologies to dw1305, whom I notice has mentioned this before on here).