Do fish need a light cycle?

[urbanfarmer]

Interesting! I'll have to try adding a light. Do you know what the deficits are from not having a light cycle? My fish are just goldfish, so they are not for eating.

From what I understand, they just grow slower. Spawning could be another issue depending on the species. Some fish may have problems with no light, but I don't know any offhand.

I have about 2 dozen goldfish that are practically sealed up and have not seen "the light of day" for almost a year (besides feeding time). Maybe fish that are naturally "bottom dwellers" would be less affected? But yea, you just want your fish to poop; so, light may not be an issue for you. I hate to tell you, but it is definitely something else... they're either sick or the water quality is poisoning them. What's your water like? Any signs of problems on the fish? How are they acting? Does your tank smell or taste funny?

[badflash]

I've never seen any evidence or read any publication that indicates fish grow faster with or without light. Light can provide important breeding cues in some species, but that is about it.

[urbanfarmer]

I've never seen any evidence or read any publication that indicates fish grow faster with or without light. Light can provide important breeding cues in some species, but that is about it.

You have it backwards, they grow slower with too much light not faster. They grow the same (normally) in 12/12 versus say 6/18. It may be species dependent.

[keith_r]

here's one study on the growth of yellow perch, best growth with a 16/8 photoperiod (light/dark)

http://www.extension.org/mediawiki/file ... _Guide.pdf

[badflash]

Povide evidence. As I said, my experience says no effect. I've never seen anyone do a study on tilapia. Please provide the reference.

I've never seen any evidence or read any publication that indicates fish grow faster with or without light. Light can provide important breeding cues in some species, but that is about it.

You have it backwards, they grow slower with too much light not faster. They grow the same (normally) in 12/12 versus say 6/18. It may be species dependent.

[urbanfarmer]

Povide evidence. As I said, my experience says no effect. I've never seen anyone do a study on tilapia. Please provide the reference.

I've never seen any evidence or read any publication that indicates fish grow faster with or without light. Light can provide important breeding cues in some species, but that is about it.

You have it backwards, they grow slower with too much light not faster. They grow the same (normally) in 12/12 versus say 6/18. It may be species dependent.

Just set up a tank with 24 on 0 off and another tank with 12 on and 12 off with all other variables equal and compare the growth rate after 6-12 months.

[aquaarche]

speaking of fish does anyone know what a good fish is to put in my grow trough that will eat the algae but not the roots of my plants?

[badflash]

Just set up a tank with 24 on 0 off and another tank with 12 on and 12 off with all other variables equal and compare the growth rate after 6-12 months.

I have several tanks with 24/7 light and several with 12/12. I see no difference. Please stop stating things you feel might be true as facts and cite some real evidence.

keith_r's reference says for one species (yellow perch), a longer photo period would be better (too bad they don't say how much).

Cite your evidence please. It doesn't help people to say reasonable things that are not backed up in fact. That is how old wives's tales get spread all over.

[urbanfarmer]

Just set up a tank with 24 on 0 off and another tank with 12 on and 12 off with all other variables equal and compare the growth rate after 6-12 months.

I have several tanks with 24/7 light and several with 12/12. I see no difference. Please stop stating things you feel might be true as facts and cite some real evidence.

keith_r's reference says for one species (yellow perch), a longer photo period would be better (too bad they don't say how much).

Cite your evidence please. It doesn't help people to say reasonable things that are not backed up in fact. That is how old wives's tales get spread all over.

Hm... irony... but you should weigh them (or some kind of measurement) not just try to "see" a difference.

I'm not stating things religiously, I was regurgitating a general conclusion from the large body of empirical evidence collected during scientific research for tilapia (as well as "textbook" information) to answer the poster's question.

[keith_r]

there have been quite a few studies on the affect of the photoperiod on fish growth..
http://www.medwelljournals.com/fulltext ... 09.760.763 for trout..
here's an abstract on nile tilapia
http://onlinelibrary.wiley.com/doi/10.1 ... x/abstract

another on nile tilapia
http://www.mendeley.com/research/effect ... ticus-l-2/

"regurgitating a general conclusion from the large body of empirical evidence" ???
sounds like folklore to me.. hehe