Backyard Shrimping Equipment: The Biofilter

* This document is a portion of the Backyard Shrimping Project. Click the "Home" button to review our effort.

The Process

Equipment and Tool List

Here is a list of the things you will need to construct your solar power system to power your pumps. We also have included recent costs and Amazon links to assist your ordering the part. Please click on the images to see the specifications and to order from Amazon as it will help fund our efforts to provide sustainable urban shrimp farming in your backyard.

Construct Biofilter

  1. Install the cleanout drain

    Cut a 2" hole as close to the bottom of the trash can as possible. Install 2" bulkhead in the hole. Glue a 2' section of 2" Schedule 40 PVC pipe into the bulkhead. Glue the 2" ball valve on the outside end of the pipe that you glued into the bulkhead.

    Backyard Shrimping: External Connections

  2. Construct and install water intake

    Cut four 6" pieces of 1/2" PVC pipe. Cut 1 piece of 1/2" PVC pipe that will reach from the bottom of the trash can to within 1" of the top of the trash can. Construct the water "cyclone" by connecting two 6" pieces of PVC with a 90° connector. Connect one end of this "L" to one connection of a 3-way PVC corner connector. Take the remaining 5" pieces of PVC, form an "L" with a 90° connector, then connect one end to a second connection of the corner connector. Arrange the unconnected ends of the "L"'s so that they point away from each other. You will connect the long piece of PVC pipe to the remaining open connection of the corner connector. The resullt will look like this:
    Backyard Shrimping: Water Cyclone
    Cut a 1/2" hole in the side of the trash can at the level that the internal "cyclone" up-pipe ends near the top of the trash can. Use a 90° PVC connector to connect the up-pipe to a 6" section of 1/2" PVC pipe that has been inserted from the outside to the inside of the trash can through the hole. Seal the opening around the pipe with RTV sealant. NOTE: see picture above for what the water inlet looks like when completed. Once you have the water piping installed, connect the water output from your water pump to the biofilter water input.

  3. Construct and install internal media support

    You want to have some space at the bottom of the biofilter to allow sediment/debris to collect. We use a PVC media support to prevent the filter media from sinking to the bottom. To construct the support you need 2 1' sections of 1/2" PVC pipe, four 6" sections of 1/2" PVC pipe, 4 4" PVC pipe sections, and 4 1/2" PVC 3-way connectors. In our case we have a wheel well that provides a ledge to rest the support on so we can eliminate 2 4" and 1 1' sections of pipe, and 2 of the 3-way connectors. Assemble the pieces to form a small "table" and insert in above the "cyclone".

    Backyard Shrimping: Installed Media Support

Install Biofilter

It can be argued that the biofilter is the most important piece of equipment in aquaculture. When aquatic creatures such m. Rosenbergii eat, they release ammonia (NH3), a chemical substance that is toxic when the levels get too high. In natural systems there are two bacteria that work together to prevent high levels of ammonia, Nitrosomonas and Nitrobacter. Here is an illustration of the chemical process (1):

Backyard Shrimping Ammonia chemical reaction

So before you introduce your shrimp to the pools, you need to establish a working, stable biofilter.

Here are the steps to establishing your biofilter (these have been adapted from (1) below):

  1. Adjust Alkalinity. Alkanity is a source of carbon for the bacteria. Baking soda is inexpensive and safe to use. Increase system alkalinity to about 150 mg/L initially. Alkalinity at this level will support the growth of Nitrosomonas bacteria, but the authors have had better success in establishing Nitrobacter bacteria at a higher alkalinity of about 200 to 250 mg/L. When Nitrobacter does become established, alkalinity can be allowed to decline to operational levels. Adjust alkalinity for bacteria: As a rule, to raise the alkalinity by 10 mg/L, add 53 grams of sodium bicarbonate for every 3,785 liters (0.117 pounds or 1.86 ounces per 1,000 gallons) of system water capacity
  2. Adjust pH if needed: Shrimp do best at about from 6.2 to 7.4 pH (2). Adding household ammonium hydroxide (see next step) will increase the pH.
  3. Provide ammonia and nitrite. As a rule, to raise the alkalinity by 10 mg/L, add 53 grams of sodium bicarbonate for every 3,785 liters (0.117 pounds or 1.86 ounces per 1,000 gallons) of system water capacity. Start with a minimal amount to allow mixing throughout the system.
  4. Add nitrifying bacteria. Several vendors supply the proper mix in both dry and liquid forms.
  5. Start monitoring the levels of the important chemical species in the water. You will need to monitor ammonia, nitrite, pH, temperature, and alkalinity. Be certain to monitor these chemical species. Research has shown that a properly establish biofilter should produce a distribution of the chemical species in your pool similar to this:

    Backyard Shrimping Biofilter Species

References

  1. SRAC-Publication-No.-4502-How-to-Start-a-Biofilter.pdf
  2. Su-MeiChenJiann-ChuChen, Effects of pH on survival, growth, molting and feeding of giant freshwater prawn Macrobrachium rosenbergii, Aquaculture, Volume 218, Issues 14, 27 March 2003, Pages 613-623, https://www.sciencedirect.com/science/article/abs/pii/S004484860200265X