Summary:

Fish have a blood pH of 7.4.

At the gills, there are only 1 or two layers of cells between the blood and the water.

Fish may become stressed or die if water pH drops below 5 or rises about 10.

pH and CO2

• If you have plants or algae (especially green water), expect a pH swing daily. carbon dioxide (CO2) is acidic. Plants consume CO2 during the day and release CO2 at night, so first thing in the morning, pH will be lower and last thing before lights out, pH will be higher. Fish also release CO2 released during respiration which reacts with water, producing carbonic acid (H2CO3), and pH is lowered.
• Carbon dioxide rarely causes direct toxicity to fish. However, high concentrations lower pH and limit the capacity of fish blood to carry oxygen by lowering blood pH at the gills.
• Airation helps increase oxygen (O2) saturation and gases off CO2.

Alkalinity (KH)

• Primarily bicarbonates and carbonates.
• Alkalinity (and GH to some degree) is what maintains pH.
• The bases associated with alkalinity react with and neutralize acids. Carbonates and bicarbonates can react with both acids and bases and buffer (minimize) pH changes.

General Hardness (GH)

• General hardness is primarily from calcium and magnesium.
• Calcium and magnesium are essential in the biological processes of fish (bone and scale formation, blood clotting and other metabolic reactions). Fish can absorb calcium and magnesium directly from the water or from food. However, calcium is the most important environmental, divalent salt in fish culture water. The presence of free (ionic), calcium in culture water helps reduce the loss of other salts (e.g., sodium and potassium) from fish body fluids (i.e., blood). Sodium and potassium are the most important salts in fish blood and are critical for normal heart, nerve and muscle function.
• Research has shown that environmental calcium is also required to re-absorb these lost salts. In low calcium water, fish can lose (leak) substantial quantities of sodium and potassium into the water. Body energy is used to re-absorb the lost salts.

Ammonia and pH

• Ammonia is more toxic at higher pH.

Heavy Metals

• Metals such as copper and zinc are more soluable in acidic water. The soluble or free ionic forms of these metals are toxic to fish. High concentrations of calcium and magnesium (hardness) block the effects of copper and zinc at their sites of toxic action. Therefore, copper and zinc are more toxic to fish in soft, acidic waters with low total alkalinity.

Copyright © 2006 theGab. All rights reserved.