Table of Contents

Obtaining Hydractinia
Setting up a tank
How to make Hydractinia racks
How to culture brine shrimp
How to care for Hydractinia
How to explant Hydractinia
How to breed Hydractinia
How to grow baby Hydractinia


Obtaining Hydractinia

We recommend researchers start with these two strains:

  • 291-10 is a male Hydractinia symbiolongicarpus colony. It was bred in the Nicotra lab from parents collected at Lighthouse Point, New Haven, CT. It grows vigorously in the lab and, for this reason, is the animal that was sequenced for the Hydractinia genome project.

  • 295-8 is a female Hydractinia symbiolongicarpus colony. It has the same mother as colony 291-10. Its father was an inbred colony obtained from Leo Buss by the Nicotra lab. It grows well under laboratory conditions and reliably produces eggs.

To obtain these strains, contact Christine Schnitzler, Matthew Nicotra, or Uri Frank and we will be happy to ship some to you.


Setting up a tank



  1. Rinse the aquarium with hot water. Then rinse with cold water and finally deionized-water (if available). Note: if you cannot rinse the tank with deionized water, then do your best to dry it out with paper towels to avoid leaving any tap water in it.

  2. Assemble the sponge filter and both powerheads.

  3. Place the filters and powerheads in a small bin filled with 29 ppt sea water and rinse the internal parts of the powerheads and filters.

  4. Place 50 ml Phos-Zorb powder into the media bag, then tie it closed.

  5. Tie the media bag to the top part of the sponge filter. (need an image of this)

  6. Place the sponge filter/media bag in the back left corner of the tank. (need an image of this)

  7. Place the 20 gallon powerhead on the sponge filter. Use a short column to connect the bottom of the powerhead to the top of the filter to ensure a good seal. Adjust the height of the powerhead if needed. need an image of this

  8. Secure the powerhead to the wall of the tank using the included bracket, which has suction cups that will allow you to attach it to the interior of the tank. (need an image of this)

  9. On the 30 gallon powerhead, insert the included air hose into the hole on the top of the diverter. (need an image of this)

  10. Use the included bracket to attach the 30 gallon powerhead to the rear interior of the tank, next to the sponge filter. (need an image of this)

  11. Fill the tank with 29 ppt artificial sea water.

  12. Plug in the powerheads and check to make sure they are actually running. Both powerheads should be completely submerged.

  13. Ensure the free end of the air hose on the 30 gallon powerhead is not submerged. If assembled properly, you should see many air bubbles coming out of the powerhead. (need an image of this)


How to make Hydractinia racks

Coming soon. For a quick start to creating 3D printed slide racks, view the instructions on the Resources page.


How to feed Hydractinia


  • Cultured Brine Shrimp
  • Plastic Carboy(s) to dispense cultured brine shrimp through the net
  • Brine Shrimp Net
  • Plastic tub(s) to place Hydractinia racks in while feeding
  • Handheld Refractometer to measure water salinity
  • Bleach


Preparing to feed:

  1. Take out the black UV lights from the brine shrimp culture buckets, rinse them with hot water to remove debris and unwanted material.

  2. Disconnect the long (5mL) serological pipettes (bubblers) from the air pump tubing and place them in the sink.

  3. Rinse the sterilized bubblers (2-3x) with hot water, use the filtering net to strain them and place them on the counter to dry.

  4. Rinse the net and hang on the drying rack to air dry.

  5. Rinse the dirty bubblers and cylinder with hot water and place bubblers into a large cylinder with the wider end at the bottom of the cylinder and the tip pointing up (we use a plastic 1000mL graduated cylinder).

  6. Add bleach to roughly 5-10mL mark then fill the rest of the way with hot water or until bubblers are fully submerged.

  7. Transfer the brine shrimp culture from the buckets to the carboys and set them on the counter next to the sink for the shrimp to settle to the bottom of the carboys. This could be done while performing other tasks. Should wait until most of the shrimp settle to the bottom of the carboy, with a concentrated orange color at the bottom. *Don’t leave shrimp in cardboys for extended periods of time as the lack of bubblers will cause them to die.


  1. Remove all plastic containers (tubs) from the drying rack and place them on two different counters to separate males from females.
    • Calculate how many tubs are needed for each side by calculating how many microscope slide racks of animals there are for each gender. (Our large tub can hold up to 3 large racks or 2 large racks + 3 small racks.)
  2. Fill each tub with water from certain tanks based on what day the water change is.
    • For example, if the feeding is happening on Monday, only use the water from tanks that need water changed on Mondays
    • Don’t forget to fill the tub with the tubes and the tub for rinsing.
  3. Submerge female and male animal racks separately in the tubs filled with water.
    • For animal slides in tubes (we use 10mL centrifuge tubes with a hole cut out of the bottom for water movement), Put them in tubs that are filled with the addition of a tube rack to hold tubes in place.
    • Prepare two extra rinse tubs for the male and female sides to rinse off the brine shrimp after feeding.
  4. If running out tub space, you can consolidate Podocoryne or non-sexually matured animals into one rack.


  1. Rinse the air-dried filtering net with hot water then again with cold water.

  2. Catch shrimp with the net (place the net directly under the carboy spigots to filter out the shrimp).

  3. Dab the net with shrimp inside out into each bin and disperse the shrimp by picking up the racks and moving them back and forth in tub.
    • For the tubed animals, you can dab the shrimp in the water next to the tube rack, and then just move the rack. The water will bring shrimps automatically into tubes through their bottom openings.
  4. When shifting between feeding male and female racks, rinse the shrimp net with hot water then again with cold water.

  5. After all the animals are fed, rinse the net with hot water and place back into diluted bleach water.

  6. Record the time the feeding started. They usually need one hour to eat.

Water Changing: (can be done while the animals are feeding)

  1. Remove any excess water to make sure all the tanks that needed to be changed only have about 75% of water left.

  2. Fill the specific “water-change only” carboy with reservoir water and add to the tanks until they are filled 100% (not all the way to the top that it will overflow).

  3. Check salinity, ideally 29 ppt, if the salinity is higher, add Deionized (DI) -water. For our tanks, 500mL of DI water will result in lower the salinity by 1ppt.
    • For example, if it the salinity reads 31ppt, add 1000mL of DI water to reach 29ppt.
  4. This is also a good time to check if there’s any excess food waste in the bottom of the tanks. If yes, you can remove them using a transfer pipette.


  1. Put racks back after 1 hr of eating. Rinse each rack in the extra tub to remove unconsumed shrimps before placing back in their tanks.

  2. Put the lids back to the tanks. For our tanks make sure that the lids are convex when put on so the curve can be counter corrected.

  3. Culture a new set of brine shrimp for the next feeding.


How to culture brine shrimp



  1. Fill the culture vessel(s) with reservoir water approximately 75% full.

  2. Connect the long (5mL) serological pipettes (bubblers) with the black plastic air pump tubes and then put the pipettes into the carboys. Make sure each vessel gets at least three pipettes and all pipettes stay at the corner position, submerged.

  3. Turn up the air pump to designated level.

  4. Measure about 15mL of Brine Shrimp eggs with 50mL Falcon Tube and funnel. Then dump the eggs into one carboy. Repeat this step for the following vessels.

  5. Put one UV light bulb into each carboy. Make sure the light bulb is fully submerged.

  6. Cover the carboys with the black plastic bag to protect your eyes from UV light.

  7. Turn on the automated timer switch for UV lights for “8 Hours”.

  8. Wash the falcon tube, funnel, and spoon.

  9. Return the eggs to the refrigerator at 4ºC.


How to care for Hydractinia

Coming soon.


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