The 'right' light wattage?

[NeilW]

I've had my new tank dry-starting for a month or so now and will eventually get round to filling it. Because of this it will have well established plant growth from the start. The tank is 17 litres. My intention was to get hold of an 11w compact fluorescent tube light but I'm doubting now wether this will be too much for my needs and I will be encouraging algae without a carbon source. Would a 9 watt compact be a better choice or would 11 be 'just right'?

Cheers,
Neil

 

[ceg4048]

Hi Neil,
It's really hard to determine "just right" for any tank. Certainly, the lower the PAR value, the better in terms of avoiding algae. In fact there is no "just right". The way that we think about light is the problem. The best analogy for light is the accelerator pedal on your car. Just what throttle setting is "just right"? The question doesn't have an answer. The lowest throttle setting is at idle. That's equivalent to the lowest acceptable PAR value (The LCP). Once you meet this minimum value then anything higher simply results in higher growth speeds. So is moving at 30mph more right than moving at 50mph? It depends on what road you're on.

If you are not using any carbon source, whether that be gas or liquid, then you're on a "C" road and you'd better be going real slow. I would first opt for the lowest power setting in a situation like this. You can always add more light later...

Cheers,

 

[NeilW]

If you are not using any carbon source, whether that be gas or liquid, then you're on a "C" road and you'd better be going real slow.

This analogy does it for me Clive, cheers. I'll try not be too reckless

I was leaning towards the 11 watt but after reading this I may go for the 9 watt. My observation was based on Saintly's low tech 15 litre that has an 11watt light, but on closer inspection he has stems whilst I do not...plus as you say every tank is different.

On the other hand I could risk it for a biscuit ...my tank is fully cycled and full of plants which is unusual for a tank when starting out.

Thanks again.

 

[magpie]

Is it possible to raise/angle the light so that while the watts stays the same, the PAR becomes less? That way you don't have to fork out on a new light...

watching with interest, given that i have a 40 litre (32 after substrate) which comes with an 18w light, plus the only place to put it in my office is by a north facing window - no direct sun, but a lot of incident light, particularly at this time of year. Dry starting (naturally ) so lots of time to see how you get on...

let us know what you choose...

 

[NeilW]

Is it possible to raise/angle the light so that while the watts stays the same, the PAR becomes less? That way you don't have to fork out on a new light...

This is a good way of doing it to find the 'sweet spot' if your using a pendant or desk lamp. However I'd be using a clip-on type compact so its at a fixed height

My original idea was to use an Anglepoise but I didn't have the heart to kill a design icon by butchering the base off (its secured with a locking washer) so its sat on my desk instead. I want my new cabinet to be flush with the sides of the glass so there wouldn't be room to stand a desk lamp next to the tank.

 

[magpie]

You could still angle sideways, no?

but that might not do good things to the deisgn iconology.

did you get a quote from TGM on your cabinet?

 

[NeilW]

You could still angle sideways, no?

but that might not do good things to the deisgn iconology.

did you get a quote from TGM on your cabinet?

As you say I think it would look a bit 'wrong' if it was at an angle I'm so particular about how things look, but I think thats the designer in me. Thats what attracted me to the planted tank stuff in the beginning was the simple lines and cleanliness of the equipment in comparison to what I used to think of as a 'fish tank'.

I got a quote from TGM of £200 plus £40 postage, which although is a fair price I can't justify that sort of money on a tank that size. The thing is its only an extra £30 for a cabinet twice as long . In an ideal world I would have had their nano/cabinet combo deal for £99 (!) BUT the shop is the other end of the country from me so driving isn't on the cards and they won't post it. Unlucky for me!

 

[bigmatt]

Could you use coloured/frosted acetate to block some of the light?
Just a thought!
M

 

[NeilW]

Could you use coloured/frosted acetate to block some of the light?
Just a thought!
M

Interesting idea, be hard to get enough light through I reckon. Could give a nice diffused look though.

 

[ceg4048]

Hi Neil,
Smoked glass (or acrylic?) would do the trick in the same way neutral density filters work.

Cheers,

 

[bigmatt]

There's an idea - use smoked glass/acrylic as a tank"lid"! Genius!
M

 

[NeilW]

Hi Neil,
Smoked glass (or acrylic?) would do the trick in the same way neutral density filters work.

Cheers,

Nice, cheers Clive. I may go with the 11 watt and the frosted/smoked glass could be plan B. I'm still torn wether to play it safe and just go with the 9 watt though . Any final thoughts to tip the balance? You are the voice of reason.

There's an idea - use smoked glass/acrylic as a tank"lid"! Genius!
M

I'm going to have to make an acrylic cat-proof 'lid' for night time so I may test this out

 

[ceg4048]

Hi mate,
Well, you know, I dislike dim tanks, and I think the 11W can work. It's unfair to say categorically that 11W can't work. You'll simply have less margin of error that's all. Remember that you can also use the Dusko approach, in addition to the other techniques, via floating plants to help control the energy penetration.

In any case, the problem is always more acute the first few months after you flood the tank. It's a tough call because we don't really know the PAR. That's why this is always such a coin toss.

I reckon you can go for the 11W knowing that you do have a few control options, otherwise you'll be forever wondering whether you could have used those extra photons.

Cheers,

 

[NeilW]

Excellent. I've also got an older 11w PL tube that I can whack in for the first few months and then switch to the newer one to avoid the time when the bulb is strongest.

I'd forgotten about floating plants which could also be a good choice to keep out the cat, I used them before and the shrimp loved the extra area for biofilm too. So I've got a few options as you say if it all starts to go wrong.

When I first fill it I won't go low-tech, but inject small doses of liquid carbon and do 50% daily water changes which should hopefully do the trick and then slow off both until it ends up low-tech.

Thanks again for some top notch advice.

 

[Anonymous]

I have 26w over my 15l nano. Don't worry too much about algae, poor water flow, low nutrients & co2 usually triggers them. You can always use some floating plants if you think it's too bright for the fish.

 

[PM]

^ ugh, that's 7Wpg, not exactly in the <2Wpg low tech/low light range...