Stress for marine-reef aquarium life?

A few of the main stress factors in a marine aquarium, (there are many others but these are at the early part of a huge list).

1.Many fish do not actually sleep in the way that we do, they scan quite easily stress while waiting for the lights to come back on!
So have a small light at the back of the tank or a couple of low light, maybe LEDs over the tank as some thing like moonlight!

2.While the lighting cycle is off over the aquarium, algae clades with in the corals cells and algae elsewhere in the aquarium will produce some co2 causing minor or major PH fluctuations, so you should have a little algae in the sump with its lighting cycle on while the tanks cycle is off to help off set this problem all marine keepers have and don’t realise until its affects are seen.
That’s why some fish when the lights come back on, have white spot.

3.Substrates in tank encourage the white spot protists and the velvet protists while in their photosynthetic stage and will over time lower the tanks over all water quality, just have a thin layer on the tanks floor if you must have a substrate.
This is a little less detrimental, have your deep sand bed or similar in the sump and the water prefiltered before it to no less than 100micron for longevity, no marine-reef aquarium ever reaches the potential it could have attained with out proper pre filtering!!

4.Do not use lighting with anything above a slight content of UVR,best with no UV radiation.
Some fish like latezonatus clown fish come from depths where there is very little ultraviolet radiation to cope with, so it will damage their eye sight and potentially cause cancer on the body!

5.While fish are under stress, whether it be a perceived or actual threat, they will stress and be at risk of death by the prolonged release of cortisol, once called adrenalin poisoning, the adrenalin word is now copy righted, so its not used as much.

6.Because fish drink an enormous amount of their surrounding waters, any nitrate or what ever substances in the water may enter the fishes blood stream or possibly affect organs exposed to this and cause them a great deal of greife, sometimes this leads to their demise by sickness or parasites from the weakening of their immune system!

7.Any conditions that the aquarium life did not start life in, will stress them a great deal, try to mimic individual’s needs to reduce stress.

8.Any prolonged exposure to nitrates, will cause slow but still serious damage to the fishes blood haemoglobin.

9.Any prolonged exposure to nitrites brings on brown blood disease and will literally poison the fishes blood making it impossible to utilise oxygen destroying the fishes nervous system, including the brain.  

All stresses unchecked lead to organ damage; immune system weakening, subsequent parasitic attacks and usually death.

The stress cortisol production can cause.

For the short term the action of cortisol production is very useful by heightening the fishes awareness enabling it to find better ways to deal with varied threats.

A term I have seen many times directly relation to this is, "stress is a physiological response to a perceived threat".
That simply means the threat may not be real, just the fish may feel threatened due to unfamiliar conditions, other tank inhabitants, location and water quality, their survival doesn't necessarily have to be at risk!
Then you have the real stress response designed to deal with more real threats, such as the threat of being eaten or placed in some other type of danger that threatens the life or safety of the fish.

This is another well-documented term that is faced by aquarium fish regularly, the fight or flight response.
This one quite often has nothing to do with any actual threat of another tank mate attacking; it will be from the fish not living in the a familiar environment that they would feel secure in knowing their territorial boundaries and recognising structures for hiding that it can access quickly if need be.

These structures (live rock-rocks) have to be of a shape and size they are used to, or they are in a perpetual state of fear of what might happen!

Normally the waters they have been placed into in have substances with in it causing them to feel sick due to constant drinking of that water and feeling out of place, it’s not enough to kill them but enough to feel not at ease with their new home and of course the stress is always there and that will kill them!
If your fish feel threatened, it would remain and deal with it or take off, right? Where does it take off to in an aquarium?
Either way, it is called autonomic self-preservation that inspires these responses!

Okay all marine fishes stress response is controlled along what is called the HPA (HPI in fish) axis, this stands for Hypothalamus-Pituitary-Adrenal (inter-renal) axis.
That means that the brain, pituitary, and adrenal glands (that sit atop the kidneys) are all involved.
Fish don’t have kidneys the way mammals do and the adrenal gland is more of a diffuse tissue spread out through the front end of the kidney from that the term inter-renal tissue instead of adrenal.

Any of the many possible stress inducers is interpreted by the hypothalamus and releases a hormone called corticotrophin and heads to the pituitary gland that in most creatures controls most hormones, in this case the pituitary will release a hormone called adrenocorticotropic this one signals the adrenal or inter-renal tissue to release a hormone called epinephrine.
This is the cause of dilated pupils, elevated heart rate, increased rate of breathing, and probably the butterflies in your stomach.
The second more long-term response is mediated by the hormone cortisol-corticosterone in some species that also comes from the adrenal/inter-renal.

Raised cortisol levels in the blood in the short term is a good thing, as it helps shunt energy away from non-essential activities to mobilizes energy reserves, redirects blood flow, etc.
In other words, the stress response is a good thing.
But as they say, too much of a good thing can be quite harmful.
If cortisol levels stay high levels for too long, important systems begin to be compromised.
Long term exposure to cortisol can suppress the immune system, reduce reproductive capacity, decrease growth rates and a variety of other actions that are considered detrimental to survival.

The body’s response to cortisol also depends on the rate at which it is being made, the rate at which it is being cleared from the system, the amount that is free in the blood relative to that which is being held by carrier proteins, the amount and sensitivity of the receptors on the cells that are supposed to respond, the overall physiological status of the fish at the time, and a host of other factors.

The next, and this is the second most common killer of your marine fish is as with before, a perceived threat or just out of its comfort zone.

Have you noticed your fish breathing quite quickly over an extended length of time, well the longer a fish has to elevate its rate of breathing, the more likely it is that a fish will go into ionic imbalance and experience osmotic shock, this is the second biggest killer of all marine aquarium fish!

The short term stress response is the most relevant to fishes survival.

Through this stress response, blood is shunted away from less critical systems like the digestive system to the muscles and brain, and energy reserves are mobilized to supply these systems with energy.

More importantly, the fish increases its oxygen uptake by increasing the rate at which it ventilates its gills and by flaring the gill filaments.

This helps with getting more oxygen into the blood, but the drawback is more of the gill is exposed to the environment.
Fish use their gills for oxygen uptake and CO2 excretion, but they also use them to eliminate ammonia (NH3) and for osmoregulation/ ion balance (we use our kidneys for this purpose).

Because fish live in an aquatic environment, they can get their ions directly from their “atmosphere” instead of having to take them in with their food or water the way terrestrial animals must.

There are special cells in the gill called chloride cells that help them do this by pumping salts either into the fish as with freshwater or out of the fish (saltwater).
Ion balance itself (such ions as sodium, potassium, calcium, and chloride) is important for basic things like nerve function, muscle function, digestion, the elimination of ammonia, and most everything else that a fish does.

If this process is compromised, the fish either takes on too much water
and its blood and other fluids become too dilute (freshwater fish) or it loses too much water and takes up too much salt, becoming too salty (saltwater fish).
This puts the fish into osmotic imbalance and potentially osmotic shock, which is a life-threatening situation.

Proper ion balance also affects the fish’s ability to eliminate ammonia and if ammonia cannot be eliminated, it could build up to toxic levels in the fish.
Subsequently the immune system collapses even more and if parasites don’t have a hold yet they soon will now that the fish is at its weakest and quite close to death any way.

Related links
http://oceaned.org/stress.html

http://www.jstor.org/stable/3881958?seq=1#page_scan_tab_contents