Backyard Aquaponics
A place to discuss aquaponics

Hi, I now have 25 trout in my 1000L IBC and verything going well. I put a ply wood lid on the tank to stop little boys from falling in, its hinged so I can feed and look in at the trout. I had a friend round to have a look and he said you can keep them in the dark they need light. Should have said the IBC has been painted black. I have since started to leave the lid open durring the day and have pad locked the pollytunnel.

Do trout need light?

No, leave the lid on or you may have trout on the ground around your ibc.

While you do need to prevent the fish from jumping out (a mesh, screen or fine netting works) as mantis said, they definitely benefit from a longer photo-period. There have been many studies done over the years that have demonstrated this. Here is one example. http://evols.library.manoa.hawaii.edu/h ... 0524/19078 that demonstrated a continuous photo-period is best for feeding and growth.

put a lif on for sure... i have lost 3 rainbows, including one of my biggest ones

One other point is that while they benefit from longer durations of light exposure to promote feeding and growth, it can be dim light. In fact, dim light is better for many species, as they like to feed at dusk and/or dawn. If you have a solid lid (i.e. wood), just drill a hole for the power cord, and put even a small waterproof LED strip underneath. That would be plenty of light.

Unfortunately, this (and many other studies) have a bias which is assuming that light IS required; the test above experiments with "normal" light, 16/8 and 24/0, but what about the "other way" 0/24 i.e. no light at all? I cannot remember reading a paper which compared growing fish in complete darkness to growing them with light, but I'm sure they'll be one available somewhere???

Maybe the question should be: With all other factors being the same, would fish species commonly found in aquaponic systems (live or grow) (better or worse) if they are exposed to (more or less) (natural or artificial) light with particular wavelengths, intensity etc? That's a lot of parameters to test in a backyard experiment!

BTW: Ever since some birds picked fish out of my FT, I have ensured that my fish are protected from the outside and to prevent them jumping out; I only block the light if algal bloom is going to be a problem, but even with heavy shade-cloth covering most of my (previous system) FT for most of the life of the fish, the fish still thrived. I have seen FTs under patios and in sheds with none, one or two translucent sheets of roofing and the fish in those systems seem to do OK too. In my current system, the fish spend the majority of their time at the back of the FT which is permanently shaded by the GB directly above them and direct sunlight only falls on the water for a very short period late in the afternoon, but of course there ambient light.



Scott

Well My Fish get about 1sq foot of Light in their tank and they seem to not be worried about it..

I found that they like to feed during the day though when there is a small amount of light..

Juergen