HOW TO PREVENT SETTLEMENT IN THE BIOFLOC TANK
For those who have been actively doing biofloc, you may have encountered some issues when running your biofloc systems, which look like this.
You'll discover these sediments in your tanks, and all of your shrimp and prawns will end up dead. In this post, we'll go over what are the reasons for this, as well as how to overcome it.
What are these settlements?
You might frequently find settlements in your biofloc tank. These settlements can be organic. They are primarily floc particles that have grown in size. They tend to settle at the bottom as a result of the biofloc process and as they accumulate density over time. One simple way to check for settlements is to use a net to scoop down at the bottom of the tank and look for any settlements that are visible in the net.
Why is this a problem?
As you may know, if there are too many sediments on the ground, the sludge will cause the shrimp to die. This is because the sludge is anaerobic in nature due to a lack of oxygen and it often causes a lot of health problems when shrimp consume it because shrimp are bottom feeders.
How can we avoid sediment?
One of the issues that industrial farmers typically face when designing their biofloc system is a lack of water in their shrimp ponds. This is one of the main issues we see with smaller scale indoor farmers, but not so much on the pond side. This is primarily due to the fact that they are using smaller or shallower pools. The reason for this is that having a high water level (about 90 cm above) causes your water to mix better. Otherwise, your length to depth ratio is off. Even when we have the same tanks with the water level lowered, it's a plural mixing in the rectangular tank and for other tanks. Our tanks are only six by three meters in size, and this issue will be exacerbated if you have a larger tank.
That brings to the second point, which is that most biofloc tanks must be properly designed to account for optimal mixing to ensure that no settlements accumulate in the tanks themselves. If you can accommodate round tanks in your system, that would be ideal. For us; alternatively, we have used a rectangular tank.
The third most important consideration is where you place your aeration. Many people place their aerations on the side, but it is actually more strategic to place your aerations in the center to achieve this core sort of teacup effect where your particles are transferred upwards and slowly close to the side going downwards. Do not place your aeration so that the flow velocity cancels each other out, causing your settlement to be all over the place.
While it may be difficult to ensure that there are no settlements in the tank because the floc's properties change over time, the only option is to manually remove the settlements. You may have a few options for removing settlements. The first step is to use a net, which can be time-consuming and difficult at times. Another option is to use settling tanks to allow flocs to settle out in specific areas of the filtration system by allowing excess floc to settle out in the settling tank. We make certain that the culture tank contains as few sediments as possible, which can cause disease or shrimp mortality. Many studies have also shown that settlements in the culture tank itself are undesirable because they cause a high mortality rate.
Allowing settlements to remain in the tank results in a 0.2 survival rate, as shown in the chart below. To achieve a higher survival rate, the best option is to always re-suspend and ensure that the biofloc system is well mixed.
Here's an example of how the settlement looks, and if you find this in your tanks, you should be concerned because your shrimps may be infected. For those who have round tanks, it may be beneficial to add more air l