no title but may be interesting - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 3 Old 01-27-2014, 05:15 PM Thread Starter
no title but may be interesting

A while back when I first added water critters to the aquarium they were very small and insecure in their new home. I thought I understood the fishes discomfort finding themselves in my world and having experienced my way of providing for their future. I was happy and looking towards the next day when everyone would be adjusted to our new life together, me and the water critters.
What a surprise I had when I turned on the tank’s lighting the next morning my new friends quickly made a mad dash to the darkest and farthest corner and huddled together anticipating a great calamity! WHAT HAD I DONE, my intent was to bring salutation and a gift of food but only succeeded in terrorizing the poor critters. After a while fear subsided and my water critter’s again ventured into the full area of the tank and began cautiously taking the offered food.

I was not sure what had just happened. My first thought was poor water condition, It’s always water chemistry, right? Wrong in this situation the problem was stress. Stress I cried! How can that be, everything is perfect the heater and HOB filter are the right size, the nitrogen cycle is established. What more is needed.

My plan for that day quickly fell apart as I worried about stressing my finned friends. Seeking forgiveness for my stress causing transgression I came across an interesting article by Byron.
In the article “Lighting: How It Affects Freshwater Fish”, Byron quickly explains that the health of all aquarium fish is closely connected to light. Not only is the intensity of the overhead lighting an issue various types of light (i take it meaning wavelength or color) as well as sudden changes from light to dark or dark to light will create stressful conditions.
Why dose changes in light have such an stressful impact on fish? The primary light receptors for water critters are the eyes. Fish eyes have rods for seeing in dim light and three types of cones that are connected to the optic nerve that transmits visual stimulation the the fish’s brain. Fish eyes are not capable of dilation where the pupil can change size, nor do fish generally have eye lids meaning fish are unable to quickly adjust to sudden changes in light. When fish are exposed to bright light the rods in the eyes retract into the retina and the cones move toward the surface of the retina and in dim light the rods move towards the retina surface and cones retreat back into the retina this process is not instant and takes a long time for the eyes to adjust to changing visual conditions, during this light adjustment periods is when the stress factor becomes apparent. One can understand becoming stressed during the light adjustment period a time when the fish is unable to trust visual stimulation and is left to respond to any stimulation by fleeing to the darkest corner where they should be able to better respond to changing circumstances.

After learning the reasons why my finned friends skedaddled when I turned the overhead lights on I began to develop a process that I thought would relieve some of the stress experienced by waiting awhile after lighting the room the tanks are in to turn on the tanks overhead lights. this seemed to have a positive results even though the water critters still fled to dark corners but after a short while my fish began to swim freely again with less evident stress.
I like the new situation that has developed so I began providing daily feeding when the over head light is turned on and then everything appeared fine. In fact things were working so well that I forgot all about the first experience of turning on the overhead lights.

Today I noticed when I turn on the overhead tank lights the water critters did not skedaddle to a dark corner but moved towards me with the expectations of getting their daily provisions. This is a different experience than what I have related.

Over time both I and the water critters have changed our behavior. I changed the time of daily provision distribution to the evening at 6 PM. Provisions are provided as soon as possible after the overhead lights come on. The overhead lights are on for only two hours daily at all other times the aquarium is bathed in ambient light.

This observation is consistence with notions Byron presents about the processes fish eyes experience during light adjustment period and only suggest the associated stressful behavior can be manipulated to a non-stressed, conditioned behavior.

Now my water critters no longer run in fear to the darkest corner but gently swim toward the surface when the overhead lighting is turned on expecting and receiving their daily provisions.
One must wonder how the change of behavior came about. Perhaps the answer is when the unconditioned stimulant (turning on the overhead lights) is paired with the conditioned stimulant (presenting food) at first caused the unconditioned response of the fish to experience stressful state but after repeating the pairing of turning on the overhead lights with the presentation of food allows the fish to associate (simple learning) when the overhead light comes on there will be food available for consumption, so the conditioned behavior is established and the new stress free behavior of swimming towards the light to get the food replaces the unconditioned behavior that was based in fear and stress.

Thank you all for taking the time to read and consider the possibilities presented.
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post #2 of 3 Old 01-28-2014, 12:56 AM
Yeah, I try to put as little stress on the fish as possible by turning off their hood lights first and then after a while turning off the room lights. This allows them to have medium light before complete darkness. There morning lights come on after they have been basked in a little bit of morning sunlight and room lights as well.
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post #3 of 3 Old 01-28-2014, 07:25 AM
that was interesting, ... i originally set my lighting to match the sun, that extra light (set to a timer) to go on shortly after sunrise, and to go off shortly after sun-set. the tank gets lots of light this way as it's by a south-facing window.

things were fine, i slowly increased the increments of the timer to keep up with the longer hours going from winter to summer.

then summer happened, i got lazy, i figured it's better to give the plants more light, ... so i left the lights on the 15 hours that was the peak of summer lighting.

i never payed attention to the fish when the light turned on, (as summer turned into winter)

currently, when the lights turn on, i am on my way to work (if i'm not already here). this makes it hard to tell how the fish are doing when the lights turn on.

during my weekend i am trying to catch up on sleep, ... new baby & a teething toddler tend to take what precious sleep you need away from you. and once more i am not present to observe the fish when the light turns on.

likewise i'm not too present when the tank lights turn off, ... kids, cleaning, etc.

yes it makes sense, i wouldn't have thought the sudden change from dark to light would be painful (how short-sighted i am) i fully expected sudden changes to their environment to be stressful, but lacked any consideration into thinking it could be painful


i do appreciate this thread immensely and when i get home will make adjustments to the timer to once again follow the dawn & dusk of the sun, ... turning on after sunrise so there is some ambient light when the lights go on, and to turn off before sunset so there is that 'cool-down' period before it goes totally dark (aside from lights inside the home)
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