CO2 + Fertilizers cause kidney damage?

[gerald]

Interesting article by Nathan Hill in PFK about potential long-term sub-lethal effects of elevated CO2 and ferts, especially their effects on kidneys. Soft-water dwarf Cichlids and Anabantoids do seem more prone to bloating and respiratory trouble than most of the Characoids and Cyprinids typically kept in high-tech plant tanks, and I wonder to what extent CO2 and ferts might be involved, either by directly damaging organs or making the fish more susceptible to infections in the organs. Anybody got further info on this?

http://www.practicalfishkeeping.co....CO2_injection_cause_disease?&utm_content=html

 

[dw1305]

Hi all,

Interesting article by Nathan Hill in PFK about potential long-term sub-lethal effects of elevated CO2 and ferts, especially their effects on kidneys. Soft-water dwarf Cichlids and Anabantoids do seem more prone to bloating and respiratory trouble than most of the Characoids and Cyprinids typically kept in high-tech plant tanks, and I wonder to what extent CO2 and ferts might be involved, either by directly damaging organs or making the fish more susceptible to infections in the organs. Anybody got further info on this?

http://www.practicalfishkeeping.co....CO2_injection_cause_disease?&utm_content=html

I think he makes a lot of valid points about the potential sub-lethal effects of prolonged high CO2 exposure.

I've been a long term member of the <"UKAPS forum">, but I'm not a CO2 user, nor ever likely to be.

Personally I'd vehemently argue that planted tanks (of any persuasion) are much more likely to contain healthy fish, and if you have a look at threads like <"Green Pekoe Pond"> and <"Congo Tetra"> you can't argue that fish health is necessarily compromised by CO2 addition.

The bit of the article I don't agree with is

Nathan Hill wrote: As plants photosynthesise, they draw carbonic acid out of the water, causing pH levels to increase. When plants respire (as they do at night) some of this carbonic acid is reintroduced back to the water, causing pH to plunge. This back and forth of acid/alkaline levels can easily prove fatal to many fish, and all too often does.

For me there are two things wrong with this.

• In a tank with added CO2 you actually get this cycle the other way around, with lower pH during the CO2 addition, followed by a rise in pH during lights out. CO2 user have both plants (and a huge amount of water movement to ensure even distribution of the CO2), so they will have high oxygen levels in their tanks (oxygen is a base).
• The changes in pH caused by photosynthesis (or adding CO2) are due to changes in the HCO3- ~ H2CO3 equilibrium, they don't effect water chemistry.

If you have really hard water you would have added enough CO2 (H2CO3 is a weak acid) to kill all your livestock long before the pH fell below pH7. If you have softer water and a planted tank then it will naturally show diurnal pH variation as the CO2/O2 balance changes.

Rapid pH changes due to rapid changes in water chemistry will effect fish, rapid changes in pH due to changes in the carbonate:CO2 equilibrium won't.

If you have a look at pH values for clear water lakes in the Parana river basin you can see there are huge pH fluctuations.

from Rocha, RRA.; Thomaz, SM.*; Carvalho, P. & Gomes, LC. (2007)
Modeling chlorophyll-α and dissolved oxygen concentration in tropical floodplain lakes (Paraná River, Brazil) Brazilian Journal of Biology 69:2

cheers Darrel