My tank is located in a room with no external window so there isn't much natural light (it's not completely dark as there is some light coming from the kitchen, but it's pretty dark). Because of the lack of natural light I have the lights timed to come on for just under 12 hours a day (so that I can see it for a few hours before I go out in the morning and when I get home in the evening), however I now have a big problem with what I think is cyanobacteria and I assume the tank lighting duration isn't helping this.
Would it be ok to program the lights to come on for a few hours in the morning, then go off, then come on again for a few hours in the evening? Or would the lack of natural daylight disrupt the fishes day/night rhythm? Should the tank be located in a room with some natural daylight?
I don't have any live plants in the tank, I'd wondered about getting some floating-type ones to try to filter out the light but I want to address location first. When I research all I can find is advice about not locating tanks too close to windows, nothing about the opposite.
The fish won't care much about the lack of natural light as long as you have a reasonable period of tank lights on in the day. Cyanobacteria can occur with excess light, but there are other factors which also promote it...high nitrates or accumulated mulm in the substrate can cause it. Also, oddly, too low a nitrate level can allow it to bloom. What is the nitrate level in the tank?
Thanks for your reply. The nitrate level is 0, the tank isn't cycled - so that's probably contributing? So the fish would be ok with lights on (morning) then period of lights off (low natural light), lights on (evening), then lights off (night)? Is there anything else I can try? I vacuum the gravel when I do water changes although it doesn't suck up everything
If the tank isn't fully cycled, make sure to do a large water change every day to minimise the effects of ammonia and nitrite.
Ammonia can also contribute to the formation of cyanobacteria. Suck out all the cyanobacteria you can see with every water change. If it's still a problem once the tank has cycled, suck out as much as possible and then cover the tank so it's in total darkness for 3 days (no light at all). Do another large water change after that and it might well have gone.
Your plan for lighting should be fine for the fish.
Thanks for the advice, that explains why my attempt to leave lights off for a couple of days made no difference to the cyanobacteria growth. I'm keeping a close eye on the water quality and hoping it won't be too much longer until the tank is cycled. I really regret not cycling it first now.