Lighting and fish maturity

[Dan Brown]

I have a friend from high school who's father is a tenured Professor at CSU (I'm writing that so you'll understand that I have confidence in the source).  He and I had several conversations about aquaponics prior to the establishment of my first system, and he mentioned that fish (we were discussing bluegills) need light to mature.  

While it seems to be widely acknowledged in aquarium groups that lighting shouldn't be a stress for the fish, avoided by using blue lights, and dimming rather than suddenly basking the tank in light, it also seem like almost all the aquaponic systems I see over 100 gallons (and many that are smaller) keep the tank in the dark.  Is that proven to be the best approach?  I love watching my fish too much to ever not at least design a window into the tank, and I think that most of the hobbyists here that started out with planted tanks would tend to agree with that assertion.

According to this article I found at rktl.fi/english/economics_and_society/food_production/projects/regu... some fish require light to avoid progressing to maturity (the inverse of what he'd told me).  I'm curious as to whether or not anyone here is using artificial or natural light in their tanks, and what the quantifiable effects on fish growth are.  I know I could dig a little deeper into the science, but I'd like to engage the discussion first so that I can direct my research towards what may apply more to aquaponics rather than aquaculture. In particular, I'm interested in the effect on tilapia.

[TCLynx]

I have read that day length and temperature both have an effect on getting tilapia to breed.

 

Now most AP system will block most of the light out of the fish tanks but that isn't the same and completely blacking them out.  My fish can tell day from night but I grow catfish, they don't need direct sun and prefer it kinda dark.

 

I actually find it easier to see my fish when I have a dark colored lid over the tank to block the reflections and allow me to see down into the water.

 

Now if your reason for wanting light in the tank is to see the fish, that might backfire if you get algae.  And avoiding algae is a primary reason for keeping tanks mostly protected from light.

[Dan Brown]

So you can just sit down, relax, and admire your work because you've got a lid on the tank to alleviate reflection?  I find that hard to believe TC.  It might make it easier to catch the fish (which I've watched your video of) but I'm talking about the meditative and peaceful state which is the primary goal of many aquarium owners when I reference being able to see the tank and the fish.  

 

Algae is a topic for another thread and not a concern, and this isn't about what I may want in a system.  Its about having another topic which has been explored in depth on this site, namely, the relationship between light and fish growth. 

TCLynx said:

I have read that day length and temperature both have an effect on getting tilapia to breed.

 

Now most AP system will block most of the light out of the fish tanks but that isn't the same and completely blacking them out.  My fish can tell day from night but I grow catfish, they don't need direct sun and prefer it kinda dark.

 

I actually find it easier to see my fish when I have a dark colored lid over the tank to block the reflections and allow me to see down into the water.

 

Now if your reason for wanting light in the tank is to see the fish, that might backfire if you get algae.  And avoiding algae is a primary reason for keeping tanks mostly protected from light.

[TCLynx]

That's all coo.  Ya got my two cents (actually I spend much time peaking under the lid of my big tank as a way to watch fish but as you noted it's how how you want to do it.)

 

Hopefully we will get some more input here to expand the topic.

[Ellen Roelofs]

I don't know about light quanitities, but I have played with photoperiod on my fish tanks a bit - to simulate seasonal patterns (to induce spawning, mostly). I keep a light on my daphnia tank 24 hours a day and they do reproduce faster than on 12/12.  I would be hesitant to keep my fish in COMPLETE darkness, or lit up through the wee hours like my daphnia... just because they're adapted to life under the sun, which comes up and goes down... circadian rhythm and all.