Three Day Transfer Method

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Introduction

The three day transfer method is a way to treat fish infected with Cryptocaryon without the use of any chemical treatments. It requires two separate tanks suitable for housing the fish, with the fish being transferred between them every three days and the tank cleaned fully.

The reason this technique works is the fish is removed from the tank before the Cryptocaryon tomonts (the cysts that form in the substrate after the trophonts are dropped from the fish) that have been released from the fish have a chance to hatch and release the theronts, which then go in search of a new host. So by continually moving the fish between tanks, there are no parasites present to reinfect it. Plus, the maximum length of time a trophont stays attached to a fish is 7 days. Therefore, after 7 days any parasites present on the fish at day zero will have dropped off to form tomonts.

Procedure

The procedure for treatment is as follows:[1]

  1. Day 0 - place fish within Tank 1.
  2. Day 3 - after 3 days (72 hours) remove the fish from Tank 1 and place in Tank 2, clean Tank 1 thoroughly and allow to be dry for at least 1 day (24 hours).
  3. Day 6 - after 3 days (72 hours) remove the fish from Tank 2 and place in Tank 1, clean Tank 2 thoroughly and allow to be dry for at least 1 day (24 hours).
  4. Day 9 - after 3 days (72 hours) remove the fish from Tank 1 and place in Tank 2, clean Tank 1 thoroughly and allow to be dry for at least 1 day (24 hours).
  5. Day 12 - after 3 days (72 hours) remove the fish from Tank 2 and place in Tank 1.

By the time the fish reaches the final step, when it is returned to Tank 1 for the for the third time, it will be totally free of Cryptocaryon.

The tank has to be dry for at least 24 hours to ensure any tomonts are killed. So this means that any biological filtration is not possible within the tanks being used, other than what is present in the first cycle for both tanks (since after that, tank will be dried and all the bacteria will be killed). Only way to get around this is to either change water to keep ammonia levels under control or transfer some biological filtration over from existing systems which are known not to carry the parasite.[1] If this last option is done, then need to ensure that cross contamination does not happen once the media has been used within one of the treatment tanks.

Variation

A possible variation on the three day transfer method is substrate removal. A layer of clean sand at about 1 to 2 cm depth is added to the tank. After three days, the sand is removed and a new layer of sand put into place. This is repeated four times. This works for a similar reason, the tomonts are removed with the sand before they can release the infective tomites. [2]

Resources

References

  1. 1.0 1.1 (http://www.atj.net.au/marineaquaria/3daytransfer.html): Three Day Transfer Method by Andrew Trevor-Jones
  2. (http://dx.doi.org.ezproxy.lib.monash.edu.au/10.1016/0044-8486(87)90041-X): Colorni, A., Biology of Cryptocaryon irritans and strategies for its control, Aquaculture, 67(1-2), (1987), 236-237.