Is This Too Much Light?

[Florin Andrei]

Regular 40 liter aquarium, 15W fluorescent full spectrum (8000K) light. 6 tetra fish, 1 small pitbull pleco. Temperature is stable at 76F. The water parameters are pretty good, here's the spreadsheet:

https/spreadsheets.google.com/spreadsheet/ccc?key=0Ah7jD_41h_eOdFRrODl3MUFQMkdZRV9FZmtaWXdtcVE&hl=en_US&authkey=CLKmnOwN

Now, there's something odd with the group of tetra. I noticed recently that in the evening they are quite lethargic. Today I had to go to work early, so at 6am I turned on the fluorescent tube on the aquarium and went to the office. At 8pm, when it's usually their dinner time, they were sitting still under the plants at the bottom, and did not come out to eat. That was worse than usual.

I was worried because I changed the water filter a few days ago, the old one was totally clogged. But I cut out a piece of the old filter and dropped it in the water pump next to the new filter, hoping to transfer some of the good bacteria. And anyway, ammonia reads zero, and the tetras started to slow down in the evening long time before I changed the filter.

But tonight, a few minutes ago (8:30pm) I turned off the fluorescent. Immediately they came out, started horsing around and chasing each other. Then it hit me - are they perhaps tired of too much light? Between 6am and 8pm, is that too much?

Normally I turn it on at 9:30am, feed them at 8pm, then turn light off at 10pm. They are usually pretty slow before I turn it off, but then there's a spike of activity after the fluorescent goes dark.

 

[Tizer]

Generally speaking you can offer light to fish for the same hours as its naturally light outside. However, you have plants in your tank according to your spread sheet, so you need to cut down the lighting to 5 or 6 hours a day since plants need rest too.

 

[Mowbz]

6am-8pm is a bit much for them, yes. I wouldnt say that its purely this thats causing them to come running out when the lights go off, but its a long time.

Your fish dont actually need a light if there is ambient light in the room. They are normally used to much less daylight in the wild, as the water is rarely as clear as it is in our tanks, so the light doesnt get through as much.

If you are planted, 6-8 hours is a good amount of light. Perhaps put the light on for 3pm (Use a cheap plug timer) and out at 10pm.

I hope this helps!

Ben

 

[Rickzayne]

I use 2 blue LEDs to put a bit of a glow from 7-12
Lights for plants 12-8
then LED glow lights 8-12

 

[Florin Andrei]

I use 2 blue LEDs to put a bit of a glow from 7-12
Lights for plants 12-8
then LED glow lights 8-12

What's the hardware that you use to manage the different lights? A simple cheap timer won't do that.

 

[Tizer]

I use 2 blue LEDs to put a bit of a glow from 7-12
Lights for plants 12-8
then LED glow lights 8-12

What's the hardware that you use to manage the different lights? A simple cheap timer won't do that.

3 simple cheap timers would. clever hey.

 

[Florin Andrei]

3 simple cheap timers would. clever hey.

Heh. Indeed.

The aquarium is in the hallway. There's not much natural light there.

I'm working from home today. Around 10am the tetras were pretty active. I turned the fluorescent on - they hid under the shrubs at the bottom. I turned the tube off around 1pm, they came out and now are running around doing silly things like tetras do. Well, I'll be darned. I learn something new every day.

Come to think of it, the little pleco was more active when the fluorescent was off, too. But I thought that's what plecos do.

Okay then. From now on, I'll keep the fluorescent on for a much shorter duration each day, 6 ... 8 hours as indicated. The hallway light will provide some diffuse illumination otherwise, when we're awake. Then dark at night. I'll look into timers.

The LEDs sound like a great idea. I happen to have two extra-bright LEDs on hand, a white LED and a tricolor (RGB) LED, for an unrelated project, I'll do some tests to see how much light they put out. Maybe I'll cobble up something, although I hate to improvise electric circuits near water; maybe I'll find something at the LFS.