The Design and Construction of a Fish Anaesthetic Machine with Divided Recirculation Systems
IAAAM 2009
Nimal Fernando; Walter Tang; Wendy Chan
Ocean Park Corporation, Aberdeen, Hong Kong


Fish anaesthesia usually involves immersion baths or for longer procedures, non-recirculation or recirculation systems.1-3 Recirculation systems described in the literature, however, only allow for the control of anaesthetic by the movement of fish or hardware back and forth to a second recirculation system, containing anaesthetic free water.

At Ocean Park Hong Kong, a fish anaesthetic machine was designed and constructed to accept a large variety of fish sizes and allow some control over anaesthetic depth.4 The design of the machine allows anaesthetic depth to be regulated by creating two separate recirculating systems-one with and one without anaesthetic. This design allows for control of anaesthetic depth without the need to move the patient or supporting hardware.

The anaesthetic machine consists of a reservoir tank, to hold the water and a trough to position and restrain the fish. Both are constructed of Perspex. Interchangeable troughs allow the machine to accept various sized fish patients. PVC pipes, taps, and a water pump drive the water through the system and regulate the movement of water through the two recirculation systems. The Perspex tank and troughs were given to an outside contractor to construct and the remaining materials and construction done in-house. The machine has been used consistently for our fish patients and the control of anaesthesia and patient set up for surgery or minor procedures was very satisfactory.


1.  Brown L.A. 1993. Anaesthesia and restraint. In: M.K. Stoskopf (ed). Fish Medicine. WB Saunders Company, Philadelphia, Pennsylvania; Pp 79-90.

2.  Harms C.A. 2003. Fish. In: M.E. Fowler and R.E. Miller (eds). Zoo and Wildlife Medicine. 5th Edition. WB Saunders, St. Louis, Missouri; Pp. 2-20.

3.  Ross L.G. 2001. Restraint, anaesthesia and euthanasia. In: W.H. Wildgoose (ed). BSAVA Manual of Ornamental Fish. 2nd Ed. Quedgeley, UK, BSAVA; Pp. 75-84.

4.  Fernando N., W. Tang, and W. Chan. 2007. How to make a fish anaesthetic machine with divided recirculation systems. Exotic DVM 9(3): 37-42.


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Nimal Fernando

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