Fluorescent lighting - can I use just one of two tubes?

[evut]

I have a large tank which comes with two T8 fluerescent tubes. I would like to try running just one of these but don't know how. The tubes are secured with plastic waterproof seals which screw over the tube where it's attached so if the tube and the seals weren't there the light fitting would be exposed. I imagine it would have to blocked off somehow. Does anyone know if it is possible to safely use just one tube?
Thanks for your help!

 

[Jesper]

Hey,
Why not use both tubes and add some more plants in the tank :happy:

I used to do what you are thinking off back in the day i.e. using just one bulb, in a two bulb fitting. If there is no button to shut off the individual tubes I would avoid it. you can always get a cheap 5 pound tube to fill the place with if you have no temperature issues that is.

There is nothing wrong with blasting the newts with daylight bulbs, they will just adjust their habits accordingly. In brightly lit tanks they might spend more times in hiding during the day and prowl during the night etc. I found that they generally adjust very well to good lighting as long as they have plenty of hides, in the end I think newts love hanging around in densely planted tanks and these sort of tanks require plenty of light. I usually go for 6500k light(daylight) with 0.5-0.75W per litre water, that can support most plants.

 

[caleb]

It depends on the way it's wired up internally, some of the newer electronic ballasts just won't work unless all their tubes are in, and are in working condition.

If it's an old-style ballast, and has two starter cartridges, you could remove one, and leave the bulb in.

If not, and if it does work OK with one tube only, you could make a fake tube from a piece of plastic pipe. If it's the same size, it should seal in the same way as a tube would.

 

[evut]

Thank you for your answers. The tank is new and the light unit is an enclosed plastic box with no (easy) way to disable one of the lights. I will probably leave both tubes in anyway because I have lots of plants and it's only 60W for 120l with both tubes. I would prefer to be running just one tube but it might not be enough for the plants. I might try it just to see if it works - thanks for the tips Caleb.

Could someone please explain how light is measured in an aquarium? I understand the fact that the water volume and the light output are measured but how does distance between the lights and the water level influence this? For example, this tank is 2x30W, 200l tank with about 120l of water, and there is about 13cm between the lights and the water. I suppose fish aquarists have full tanks of water so it's never mentioned...

 

[Jesper]

Well, it is very far from an exact science in most cases... Most ppl do not bother with distance calculations, obviously you would lose some energy, but I think if it is hanging 13cm from the tank it is not worth calculating the loss. The difference between .5 and .75 W per litre is much greater than the loss from the distance and that is just a rough guide anyway.

Obviously behind those general recommendations(given to me as 2 to 3 W per american gallons( 3.8l }} are things like light source distance to object, light intensity, depth of the tank, surface area, surface reflections, diffraction, incoming sunlight etc, one could spend a lifetime optimising and some ppl do...

The light temperature is important though, it is measured in Kelvin(Kelvin is Celsius + 373} and based upon how warm an object would have to be in theory to emit a certain wavelength of light. Most everyday bulbs have a light temp at around 3000 Kelvin, that does not do anything for plants since the sun averages about 6500 Kelvin during midday. If you use a 3000 Kelvin light temp you are basically just heating up the tank.

So I would say that your 60W at 13cm sounds good if the bulbs are somewhere between 5000 and 10000 K. I just set up my tank with ca 1W per litre, 6500 K, bulbs are 14cm from surface and it gets plenty of daylight ... That is overkill, especially wo CO2 and I will most likely have algae very soon... But it looks so pretty!

Tank is sitting in the window sill and when it gets dark(4pm} it looks just like midday light coming in from the other room. It really messed up my timekeeping the other day....

Hope that helped.