Having enjoyed the Holiday weekend and seen some really spectacular fireworks displays, I thought I might start a few fireworks of my own with the following discussion. There are practices in the aquarium hobby that almost everyone follows, but sometimes I think it is for the wrong reason or else the explanation is lacking in facts.
The first “rule of thumb” I would like to discuss is the use of the actinic lighting as a sunrise/sunset effect on a mini-reef aquarium. When hobbyists have a lighting system of multiple bulbs and can control different groups, they often schedule the blue actinic bulbs to come on a few hours/minutes before the daylights to mimic a sunrise, and then keep them on after the daylights turn off to mimic a sunset. To the human eye, this makes a good effect, and we think we are allowing the fish and corals to slowly adapt to the light before the daylight bulbs kick on. Assuming the total output (in watts) is nearly the same between the actinic and daylight bulbs, you need to remember why we are using actinic lighting in the first place. The blue wavelength of the actinic bulb penetrates the water deeper than the daylight, and the corals have adapted to be able to absorb this wavelength better. Therefore, the actinic bulb is “high noon” for the corals, and the daylight bulbs are much less intense, so our attempt to have a slow sunrise is actually jumping into high noon from the start. Admittedly for most applications, the aquarium is in a room where there is a fair amount of ambient lighting before the aquarium lights come on, so it is not as is if we are going from total darkness to high noon. Also, if you are using a combination of Metal Halide daylight bulbs and fluorescent actinic bulbs, then it might make more sense to use the actinic for sunrise/sunset. This may cease to be an issue with the newer LED systems that are starting to come with “ramp timers” that allow us to control the actual intensity of the light more so than just the spectrum. On a side note, I have tried to find out if the fish’s eye has also adapted to see the actinic wavelength as a brighter light but have not found any article/study to prove this. It stands to reason that the fish eye would also have an adaption to “see” the blue wavelength better since they live in the same environment, but it may not be so. I found one article that reported to show what other fish look like to each other and the colors we see are not at all what the fish sees. Some of the brighter colors actually fade away and make the fish harder to see!
My second topic comes about from a discussion I recently had with a hobbyist over the advantages/disadvantages of various bio-media. I know this is a bit of a nitpick, but I have always had a bit of an issue with the way the Bio-Wheels were marketed. Make no mistake, Bio-Wheels have many advantages over most other bio-media, since the design of the system allows better use of all of the surface area (and there is a massive amount of surface area per wheel) and also prevents the surface area from becoming clogged with detritus from the wastes. Also, the design allows the “shedding” of excessive bacteria to keep the colonies constantly growing and increasing their efficiency. Compared to any of the totally submersed bio-media found in canister or power filters, the Bio-Wheel growing surface area will be exposed to completely oxygen saturated water. But this is my point of contention. Some argue that since the Bio-Wheel is exposed to the atmosphere and it has an oxygen content of nearly 21% versus the water saturation (temperature dependent) level of 6% to 7%, that the oxygen content of the water around the bacteria will also be higher. I am afraid not, as the oxygen still has the same ability to diffuse into the water covering the bacteria. The advantage would be that it will always be fully saturated, unlike submersed bio-media that may be in a flow of oxygen deficient water. As I said, this was a bit of a nitpick!
If you have a topic of contention you would like to share, or wish to take me to task for my opinions, please write and let us know.