In ponds, ammonia is produced by excretion of fishes, crustaceans, microbial decomposition of organic materials, urea and ammonium fertilizers, supplementary feed etc.
Unionized ammonia fraction is more toxic to fish. A concentration of 0.02-0.05 mg l-1 of unionized ammonia is safe for fishes. The concentration of unionized ammonia increases with increasing pH and temperature and at higher concentration it is highly toxic to fishes.
In an established pond with a functioning filtration system the ammonia is broken down by Nitrosomonas species of bacteria to a secondary product, known as nitrite. Ammonia can exist in two forms when dissolved in water, the first is the free ammonia and this is very poisonous to fish, the second form is known as ionized ammonia which is not quite as harmful as the free form.
Besides pH and temperature, some other parameters are also having indirect effects on the ammonia toxicity-
- Ammonia is more toxic when dissolved oxygen concentration in fish ponds is low
- Toxicity of ammonia decreases with low pH and increased CO2 concentration in fish ponds
- Toxicity of ammonia decreases slightly by high concentration of calcium
- Stop fertilizer and feed application after reducing stocking density.
- Stop using lime and control pH, as higher pH favors ammonia toxicity to fish.
- Exchange 30 – 50 % of water, if possible.
- At the preliminary stage table salt @ 80-100 kg /ha / meter water can be applied.
AirOxi Tube base aeration system works on diffusion principle. The bubbles of air rise up and oxygen dissolves in the water during this process. An additional benefit is also that while the bubbles rise, they also diffuse the ammonia trapped in water. Thus, this cycle helps in balancing the ammonia in the water. AirOxi Aeration System is not just good for increasing the DO, but also reducing ammonia levels in the aqua system.