Systems - The Structure
Time To Wake Up!!!
Written by Wednesday, 02 May 2001 01:00
How do you wake up your fish? As you may not know, the sudden addition of 200+ Watts of light in a previously dark tank may increase the stress of the fish. You can readily see that by watching their sudden nervous moves, every time this takes place. Of course, in nature, this takes place gradually and it takes some hours before the Lake receives a fair amount of sunlight. Things are further complicated for Malawi haps which use to live at depths over 10 meters. At that depth, the increase of light is even more gradual while its intensity never reaches the average light intensity of a tank. This is evident in all video tapes I have watched and it should be replicated in our tanks. These species are adapted to moderate / low levels of light intensity and this is how we should keep them if we are to meet their natural needs. We can still have a fair amount of light so we can adore them yet excesses are to be avoided. What is perhaps more important is the quality of light that you use. It goes without saying that the cheap lamps we use in our living rooms will never show the true colors of the fish since they may seem white but they are actually "green". You have to use special aquarium lamps but you have to be very careful as to which ones you choose.
The normal "freshwater" tank lamps (I am always referring to fluorescent tubes) are not ideal since they are very warm. They are ideal for lighting an mbuna tank or a planted tank because they will bring out the warm colors (red, orange and yellow) and make a nice contrast with green plants. However, Malawi haps live at depths of 10 or more meters. At this depth most of the warm rays have been absorbed leaving a great amount of blue. So the correct ratio (if we assume we could actually mix the colors ourselves) would be some warm colors (red, orange, yellow) and a big amount of cold ones (green and most important blue). Of course, such a lamp doesn't exist. However we can combine lamps to get the desired effect. The best solution color wise is to use a combination of actinic lamps (very narrow spectrum, blue color) with sunlight tubes which emit in the red, green and blue. I have found out that two combinations work best. You may try a combination of white marine tubes rated at 18000 K with actinic tubes at a ratio of 1:1. Alternatively you can try the more penetrating white marine lamp rated at 8500-9500 K with actinic lamps at a ratio of 1:2 (two actinic tubes for every white one). In order to avoid colored areas in your tank you must arrange the lamps very tightly, preferably at the center of the tank's width. I have a two side open tank so this is mandatory but I have also tried it on "normal" tanks.
I currently use 1 row of white lamps with two rows of actinic lamps (the white lamp is the center row). This combination creates enough light to enjoy your fish yet the atmosphere is far more natural. When I compare the "atmosphere" of my haps tank to that of the mbuna, the latter seems like the sun is directly over the tank, while the former has a "deep water" feeling. Of course, in order to replicate the exact conditions that exist in nature one has to use much less light but then you will have to guess where the fish is.
As said, awakening the fish should be done gradually, in a mild way. The best way is to use timers. My tanks first receive the daylight which comes through the windows (not enough to stress the fish, keep in mind that it increases very gradually). When the natural light is at its maximum (see photo below) the interior if the tanks is still very poorly lit.
Then the two actinic rows go on. The intensity of the light almost doubles. This series of photos was taken without a direct flash unit in order to show the conditions that exist in the tank. The one at the top was taken in the morning with the ambient daylight. The flash unit was pointing at the ceiling (otherwise there would be nothing to show you). The fish are still sleepy as you can see. In the photo below, the actinic lamps are on. The room was darkened so the tank is shown as it looks like (well, as closely as possible, it looks a bit more blue in reality). Again no flash was used. I chose a fast film (800 ASA) for this series of photos because using a flash unit would "kill" the blues. The fish start to swim and act normally although not very active. The tank will stay with this kind of light for an hour.
Then the white row goes on. The last photo was taken from exactly the same spot with the same settings on my camera. You can now see how "natural" this lighting is. It is true that the blue color is even more natural (as far as the total intensity is concerned) since you are not supposed to see so much light at a depth of 20 meters, no matter how clear the water is. However, an overall actinic blue is not pleasant to the human eye which has a difficulty to focus. Moreover, because the wavelength is shorter in the blue rays, the dust particles and the small air bubbles make the water seem dirty (they become secondary light sources; millions of them). Therefore, since the task is to enjoy our fish, the addition of the white row is mandatory. In my opinion, the bottom photo has already too much light for deep water fish. However, this is as little as you can go - I use just one row of white tubes. If you want to go even lower, you can try one row of white lamps rated at 18000 K, which is less penetrating. The tank height is a generous 70 cm which causes much of the light to be absorbed. The white lights will stay on for about 7 hours per day. When they go off, the blue lights will stay on for another hour and then the tank will be completely dark for the night.
Observations: I can't claim that the fish like this lighting more than the normal all white one as far as their "day" conditions are concerned. I haven't observed any differences in their every day activities either. It may be said that they accept both chromatic combinations equally well. However, there has been a markedly different behavior when their "day" starts which can be described as less nervous movements and "panic" reactions when the blue or white lamps go on. It is evident that the transition from the "all dark" to the "ambient filtered daylight" and then the "deep blue" environment is better accepted by the fish than the sudden "all white" environment. Indeed in such a change the fish show a "stress" condition which is gradually reduced over a five minute period. This "stress" condition is much milder (or does not exist) in the deep blue - white transition.
Of course, an even milder (more gradual) transition would be much preferred. With the use of timers this is easily done. However, the limiting factor is the rows of lamps used. In my tank only one step can be added which would result in a "all dark" - "ambient filtered daylight" - "very deep blue" - "deep blue" - "white" sequence. Special care should be taken to make sure that the light levels created by the ambient filtered daylight are considerably lower than the "blue" stage. During the winter months this is not a problem because the course of the sun doesn't allow its rays to reach my tanks. However, during summer months I have to keep most of my windows closed with their covers on, to make sure that no direct sunlight reaches my tanks.
Hobbyists with well lit (usually planted) tanks would certainly benefit from this approach since in such tanks, the presence of as many as six rows of tubes is common. In such a tank the hobbyist can use six timers and create a much better simulation of "dawn" especially if he uses warm and cold colored tubes. In such a case he could create an "all dark" ⇒ "deep orange" ⇒ "light orange / red" ⇒ "white" sequence which would resemble "dusk" when reversed at night.
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