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This thread is exactly why I am happy that apistogramma.com exist! Thanks to all involved in the discussion. And hopes that the OP post soon that he has tons of healthy fry!
Keith Chitwood
Keith Chitwood
The water companies do the same thing in the UK, they inject NaOH and add a phosphate compound, the aim of this is to reduce the likelihood of the water gaining lead or copper ions from the pipe work. Technical term is "PIMS", phosphate induced metal stabilisation for control of "plumbosolvency". <http://www.edie.net/library/view_article.asp?id=1814>.The high pH in the water is due to NaOH
I know what you mean, but we have to be very careful with the term "buffer", as it has a precise chemical meaning <http://en.wikipedia.org/wiki/Buffer_solution>. This should really should read:NaOH the city use to buffer the water
I don't think the H2SO4 had any specific toxic effect either, I think it is do with the lack of DOC from not having humic compounds etc. The DOC will chelate trace heavy metals and possibly interact with any trace pesticides that might be present in the water, and that the fry may be especially sensitive to. If it is a chelation effect a water conditioner with EDTA should also reduce fry death, although this wouldn't work if there was lots of iron ions (Fe3+) present (FeEDTA is the most stable form).I find it puzzling that the adoketa fry would die in a couple of day. Somehow, I dont think the use of H2SO4 has anything to do with it. To test this, you can switch out the H2SO4 with H3PO4 to lower the pH, which basically replaces the sulfate with a phosphate.
....... A solution at a given temperature has a limited capacity to contain gas (cooler liquids can contain more). So you cannot simply increase the aeration when adding CO2 in order to increase oxygen content...... One of the reasons CO2 causes problems for fish is that it is MORE soluble in water than O2 is. Whenever a gas has the ability to chemically combine with another molecule in the solution (in this case CO2 is combining the the water itself), the solution can hold more of the gas. CO2 + H2O = H2CO3 (carbonic acid) O2 does not have the ability to bond with water, so it is not as 'soluble'. The attraction between CO2 and H2O forces an unequal rate of diffusion of gas into the water. That means that if CO2 and O2 are presence above the water in equal concentrations, the CO2 will diffuse in faster than the O2 will... resulting in a greater concentration of CO2 than O2. The reason we 'inject' CO2 into planted tanks is that the atmospheric concentration of CO2 is naturally much much lower than that of O2.
So this applies to oxygen, but not to CO2 because it doesn't behave in accordance with Henry's Law, as some proportion of it will ionize according to the carbonate/carbonic acid equilibrium. The maximum solubility of CO2 is 1,700ppm.At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
If the concentration of CO2 does not affect the concentration of O2, then we would never reach a point where the fish asphyxiate when injecting CO2... but that happens, and the damage cannot be attributed to pH drop alone. I have done some diagnostic problem solving on a planted tank with gasping fish. The CO2 being injected was increasing CO2 significantly and the keeper was not turning the CO2 off at night. He would wake up in the morning to fish gasping at the surface. Within a few hours of the light being on, all was good. His pH in the morning was measuring 7.5, because his KH was high enough that the pH drop from CO2 injection was contained by buffering. Could it be that the CO2 that reacts with water does not follow Henry's Law, but not all of the CO2 combines with water? And that the CO2 that does not react to make H2CO3 does follow Henry's Law and thus result in a reduction of the partial pressure of O2 in the water?
Also, bubbles of injected CO2 are at higher pressure than the air above the tank, and a CO2-injected aquarium is NOT at equilibrium