Probiotic bacterial cultures brought to shrimp ponds usually are composed in general of heterotrophic bacteria or a mixture of heterotrophic bacteria and autotrophic nitrifiers. Heterotrophic bacteria are the ones bacteria that usually reap their vitamins from natural assets. The primary source of carbon for those bacteria is carbohydrates. Nitrogen is commonly obtained from the proteins inside the organic fabric consumed through the micro organism. Just like the shrimp, heterotrophic micro organism excrete ammonia as a by-product of the metabolism of the proteins they eat. Some heterotrophic bacteria, but, are able to make use of ammonia immediately as an alternative source of nitrogen.
What does this all have to do with C: N ratios? Shrimp feeds used in intensive shrimp ponds typically have as a minimum 35% protein. These feeds do not comprise a variety of carbohydrates. C: N ratios in these feeds typically run round 9:1. The micro organism require approximately 20 gadgets of carbon according to unit of nitrogen assimilated. With this kind of low C:N ratio inside the feed, carbon is the proscribing nutrient for heterotrophic bacteria populations. The bacterial population will not extend past a sure factor due to the constrained availability of carbon. The protein within the organic detritus supplies most of the nitrogen requirement for the heterotrophic micro organism under these occasions, and inorganic ammonia isn’t always applied as a nitrogen source to any excellent volume.
If the C: N ratio is increased, either via feeding lower protein feeds with a higher percentage of carbohydrate, or by way of adding a carbohydrate source which include molasses similarly to the ordinary feed, the elevated availability of carbon allows the heterotrophic bacterial populace to eat a higher percentage of the protein within the natural fabric. This effects in a entire digestion of the natural cloth within the pond through the heterotrophic bacteria. As the C: N ratio will increase, the heterotrophic micro organism resort more and more to ammonia metabolism to satisfy their nitrogen requirements. As C: N ratios are elevated even further, a factor is reached where nitrogen, as opposed to carbon, turns into the proscribing nutrient. At this point, ammonia concentrations have to be near zero mg/L in the pond.
It need to be talked about that keeping the feed protein constant and supplementing with natural carbohydrate will result in much higher bacterial counts inside the pond. The oxygen required to support this additional bacterial biomass will growth proportionally with the growth in bacterial population. Likewise, CO2 production will boom, using pH down. If you are deliberating carbohydrate supplementation to growth C: N ratios, ensure that your pond is well-aerated and circulated to keep the natural detritus suspended inside the water column where there’s enough oxygen for the heterotrophs. Also, once you increase a dense populace of heterotrophs thru carbohydrate supplementation, don’t discontinue the carbohydrate supplementation . This will starve the micro organism of carbon, a die-off will occur and you’ll get an ammonia spike