Decapsulation Why?
By Tracy Warland
The dehydrated shell is usually put through a process called decapsulation:
removal of the hard outer shell. These cysts are often referred to as decapped cysts.

The cyst must be re-hydrated prior to decapsulation. This is done by simply adding your cysts to water for about 2 hours.

Adequate aeration is required during this re-hydration period to ensure the cysts stay in the water column.

The cyst (brine shrimp egg) have several layers: first is the chorion-this is the hard outer shell that protects it during its dormant periods. The only way to remove this shell is by oxidation with hypochlorite solutions-such as bleach.

The second layer: the outer cuticular membrane allows movement of small molecules. While the third layer Embryonic cuticle is the hatching membrane we are left with after decapping, this membrane is the one they hang onto during the final stages of hatching.
There are several reasons why decapping is commonly done:
  • The hard cyst shell (chorion) is not digestible and can lodge in the gut of small fish fry causing obstructions - this nearly always results in death.
  • Cysts shells can be contaminated with bacteria and pathogens, this procedure disinfects them and eliminates these problems.
  • Separation after hatching of the hard shell and the live brine is a very tedious and frustrating job. After decapping the hatch is cleaner.
  • The hatch time is usually slightly shorter and the hatching percentage rates are significantly higher.
I have always found it easier to decap a larger amount than needed and then store them for future use.

Because you usually purchase your cysts in a dehydrated form, they must be re-hydrated before you can decap them.

To do this, they are placed in some water (tap water is fine), aeration needs to be added to keep them circulating in the water column.

After about 2 hours your cysts should look nicely rounded.



There are a couple of important rules to observe when decapping:

  • The cysts MUST be re-hydrated before adding the Sodium Hypochlorite solution.
  • Do not try to decap more than 100 grams of cysts as the temperature rise will kill the cysts (ice can be added to the vessel just before adding the sodium hypochlorite to help with the temperature rise).
  • Do not exceed the rate of 10 grams of cysts per two cups of water (500 ml)
  • A desired concentration of 22 g/L of active hypochlorite solution is required for a successful decap.
  • Cysts need to be de-chlorinated immediately after decapping to stop the process or the cysts will be useless.
  • Aeration must be used throughout the whole procedure to keep the cysts moving in the water column.
  • Use a hatching vessel that holds twice the amount of hydration medium (water) you are going to need.
  • A vessel with sloping sides works best as there are no "dead" spots for cysts to sit.
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