Do fish need a light cycle?

[urbanfarmer]

About your new avatar...looks about right, but the hair needs to be more curly... :P ..

Maybe it will straighten out some when I get old!!!

from what i've found over the last few days, is that the photoperiod is an important factor in growth, and there have been studies done with several species w/ different lighting times..
i've concluded that i'll investigate whatever species i'm growing, and figure out what works best for me..
i've been contemplating working with my yp and trying to induce a spawn this winter.. just picked up a free 55 gal tank, so i'm up to 5 tanks, and the pool.. but i gotta get my gb's on line before i do much more

Yea, it does depend on so many factors. Light intensity, spectrum of light (there are studies on just the colors, weird but interesting), and probably things not studied like UV. Fish species, stage of life cycle, even genetic factors.

Those new plasma lights mimic the spectrum of the sun pretty well, but nothing will match the sun's intensity.

Most spawning studies appear to be done with low intensity lighting. I think this all comes from the earlier studies in the 1950's when they associated spawning behaviors with the extra light from the moon during seasons.

[badflash]

Bristle nosed plecos are the best for clean-up. They clean up well, and only get to about 4".

My conclusion about photoperiod is that on its own is does very little for the fish. It can make an abundance of food in the wild which can then contribute to growth. In an aquaponic setting, it isn't worth much for the fish, but could help your plants.

UF, I find your deflecting comment quite curious. Please site some examples, or is this another of your deflections?

[urbanfarmer]

I posted the references at your request, did you check?

My conclusion about photoperiod is that on its own is does very little for the fish. It can make an abundance of food in the wild which can then contribute to growth. In an aquaponic setting, it isn't worth much for the fish, but could help your plants.

Okay... but, 24 hours of light is clearly not good for some animals and the research cited states 24/0 cycle slows growth in tilapia under long term grow out conditions. Is there a reason you are still stating contradicting statements without proof in lieu of the ample empirical evidence????

[badflash]

I appreciate the overload of data. I was asking for examples of me deflecting, not more data.

I never stated that 24/0 was beneficial. I stated I don't think it matters all that much, and isn't worth the effort. In the cases I read with tiliapia involved the photoperiod it did not significantly effect growth rate when isolated from other factors. It will take me some time to read through your list.

As I have said, I see little or no difference between my fish that are 24/0 and ones that are 12/12 or 0/24. Did you find one of the ones you cited that show it does make a statistically and economic significant difference?

[urbanfarmer]

I appreciate the overload of data. I was asking for examples of me deflecting, not more data.

I never stated that 24/0 was beneficial. I stated I don't think it matters all that much, and isn't worth the effort. In the cases I read with tiliapia involved the photoperiod it did not significantly effect growth rate when isolated from other factors. It will take me some time to read through your list.

As I have said, I see little or no difference between my fish that are 24/0 and ones that are 12/12 or 0/24. Did you find one of the ones you cited that show it does make a statistically and economic significant difference?

[...]

[urbanfarmer]

With regards to your other point, if there's no benefit between 12/12 and 24/0, great! If there is, I would like to know about it and maybe WHY if there is research into it. You make a good point about significance. It may not be a significant difference, which makes it nearly trivial. However, when modern research states it is significant it is with a high degree of certainty (P = 0.05). From there we have to examine the cost for a commercial operation or the convenience for a hobbyist situation (sometimes the cost too). I'm sure if David could grow fish twice as fast by screwing in a 10 Watt CFL bulb and keeping it on at night, he would go for it.

Of course my first point in all of this is that you get optimal growth at 12/12 and that 24/0 hurts growth. Light doesn't make tilapia grow fast, but too much light slows their growth. Your FCR (feed conversion ratio) starts to drop as well meaning you have to feed them more to sustain growth.

So you see, through these exchanges of ideas supported by empirical data we can all learn, and I have learned a lot from most of my exchanges on here. But, you need to learn not to discredit someone else so quickly if you are not willing to support your claims. If you have a formal education in aquaculture, fine, but to my knowledge you do not. I myself have only taken a few courses in aquaculture, but many more in botany, soils, chemistry, biology, etc. The only times I state something as fact without reference is because I learned it out of a TEXTBOOK (not a regular book). The difference is, textbooks reflect our generally accepted principles in science, which means there's hundreds if not thousands of research studies published on it, and usually it represents decades if not centuries of scientific progress.