Fish respond to stress on three levels. This integrated stress response includes: primary, secondary and tertiary levels. The primary response is the release of the stress hormones, corticosteriods and catecholamine, into the bloodstream. The secondary response is the effects of these hormones at the cellular level including the mobilization and reallocation of energy, osmotic disturbance and increases in cardiac output, oxygen uptake and transfer. The tertiary response extends beyond the cellular level to the entire animal. It inhibits immune response, reproduction, growth and the ability to tolerate additional stressors (Bartelme, 2003. Pickering, 1987. Maule, et al, 1989. Barton. et al, 1986. Mesa, 1994).

 

HOW DOES ALL OF THIS RELATE TO PIRANHAS IN THE HOME AQUARIUM?

 

Present research does indicate that no matter how calm your fish may appear in a home aquarium, it is having some type of stress. It's unavoidable. The degree depends on what you are doing, have done, or continue to do. Where there is little to no activity outside the aquarium, the fish is very aware of vibrations that filter through the water. Whether its a door slamming in the background or you drop something on the floor the water is the conductor of those vibrations to the fishes sensory organ. Water chemistry can all effect the stress level, to include temperature changes. Introducing food or even a new tank mate can also lead to stress for the piranha. According to Dr. Shawn Prescott who wrote an extensive article on this subject, he had this to say:

 

Compare this to the typical Aquarium. Some of us do change a percentage of the water in the Aquarium, usually about 10% (if we do) weekly. Many do not even do this.

Instead of a natural ecosystem to manage the various subtle changes that are bound to occur, when we keep our specimens in an artificial habitat, we rely upon filters, often changed infrequently, UV's to kill off as much as can, Ozone to purify, chemicals to supplement what we think needs to be replaced, ( the evidence for such replacement is too often questionable).

It's rather like asking us to feel good in the rather aseptic environment of a hospital ward. Probably alright, (some today even question that), but it hardly leaves the average person feeling that they would like to go there as they felt so good in that atmosphere. In both freshwater & marine environments there are many forms of natural plant life . Many of these act as part of the food chain either directly for the fish, or indirectly by contributing to other forms of life which eventually are eaten by the fish.

I know of no "plastic" forms of plant that exist in nature, but far too many of our Aquarists seem to think that this artificial media, looks nice and is useful. I personally would seek to disagree.

Furthermore in many of revered Public Aquariums, I have seen the same plastic rubbish replace the real thing, as evidently the professionals who are employed to run these Mecca's of entertainment are not provided with the means by their money masters, to achieve what should be for so many good reasons an essential educational tool.

If one talks "off the record" to many of the Curators of too many Public Aquariums, you may be horrified to hear just how often they have to replace their fish etc. In some cases the record is as bad as Aquarists who have little or no experience. So much for conservation of Nature.

Again the reason is in many cases, that to create a stress free environment is one that requires a great deal of expertise, planning & the funds & personnel to make it work, on a long time basis. When this is absent, whether it be in a Public Aquarium or one in our home, then stress is a typical consequence, & fatalities are to be expected, as disease manifest itself.

 

SO WHERE DO WE GO FROM HERE?

 

In conclusion, try to make your fish as comfortable as possible in the home aquarium. Try to avoid the trap of confining too many in a given space. Practice good fish husbandry and above all else, do not be fooled by the mind's eye that just because your fish looks fat and happy, reproduces for you, that all is well. They are not living in a total stress free environment, contrary to what you are thinking or seeing. To consider otherwise is nonsense. Be watchful for situations where the fish is near air bubbles or streams. This may indicate a problem with the respiratory system. Young fish tend to find places to hide and aerators often do the trick in providing them a curtain to hide behind. Some species like S. rhombeus require heavy flow (oxygenation) and in my opinion on observation, they do better with a suitable powerhead. They are deep water fish often found near rapids and this addition will help the fish exercise more and respire better. 

 

Another thing to consider is the body color darkening, respiring heavily, and clamped fins syndrome. If you see your fish do this, then very likely your fish is suffering some type of illness. Immediate treatment should begin once you have correctly identified the actual problem. Lastly, don't be afraid to ask other more experienced aquarists for help in determining fish problems. It can help solve your fishes problem and perhaps save its life.