• You are viewing the forum as a Guest, please login (you can use your Facebook, Twitter, Google or Microsoft account to login) or register using this link: Log in or Sign Up

Lighting a 30" tall tank

Hi,
You're barking up the wrong tree if you think you need 400 watts of lighting for a 30 inch tall tank. The problem for carpet plants with 30 inches has nothing to do with lighting and has everything to do with getting flow and CO2 to penetrate to that distance.

Cheers,
 
Well the plan is to use a FE with a 2000 lph external. For the CO2 I was either going to introduce it via the filter inlet or alternatively blast it around via a seperate internal pump.

Back to the lighting I think I would like to stay clear of halides if possible, are the LED lights a non starter? They seem to be more for corals and I am thinking it might be too much of a marine blue sheen?

Rgds
 
Hi,
I don't see any reason to avoid halide lighting at all, or LED for that matter. You can get any color you like. The problem with LED has more to do with cost and the problem in general with both halides and LED is that people think they need high wattage. All types of lighting can be used effectively as long as one does not overdo the energy levels. If the lighting unit will be at a fixed distance, then it's important to keep to the general WPG guidelines.

More importantly, you need to have a way of getting CO2 down to the substrate. This is actually a much more difficult task than you might imagine. Lighting is easy, flow/distribution not so.

Cheers,
 
ceg4048 said:
Hi,
I don't see any reason to avoid halide lighting at all, or LED for that matter. You can get any color you like. The problem with LED has more to do with cost and the problem in general with both halides and LED is that people think they need high wattage. All types of lighting can be used effectively as long as one does not overdo the energy levels. If the lighting unit will be at a fixed distance, then it's important to keep to the general WPG guidelines.

More importantly, you need to have a way of getting CO2 down to the substrate. This is actually a much more difficult task than you might imagine. Lighting is easy, flow/distribution not so.

Cheers,

Well the LED system linked in my O/P is quite cheap but I am unsure if really suitable for plants, I appreciate what you are saying about the importance of getting the flow correct on the Co2 but the lighting represents the largest outlay so I need to make the correct purchase.

I would have thought a 200lph filter combined with an additional pump would be adequate circulation but then again I could be talikng rubbish. The feedback I am getting is that there is a massive difference in succesfully achieving a 30" tall set up against a 24" set up, would you say this is the case?

Rgds
 
Ceg is normally right on most matters but I must say I would of thought you would need more than the average light source to get a nice tight carpet of HC at 30''.
The general idea is to use the minimum amount of light to get good results & I am not sure if T5s would give you that?
A lot of folk rate these for growing freshwater plants http://www.aquaessentials.co.uk/tmc-gro ... -3800.html
The main issues with trying to achieve a beautiful algae free planted tank do revolve around light but around C02 & its distribution & certainly on shallower tanks 2 x T5 are very adequate.
 
Hi,
All lighting is suitable for plants. If you can see the light then it's useful. The difference between the various technologies of light is simply the percentage of the energy produced by the bulb which is light and not heat or other form of radiation. For example, the energy output of a typical incandescent light bulb contains 15% light and 85% heat (infrared). The plants will use that 15% but that means a 100 watt incandescent bulb is only producing 15 watts of useful light, so it would be very inefficient to use these bulbs. All this means is that they are not efficient, not that their light output is irrelevant. The energy output of halide/HQI and so forth is somewhere around 40%-50% visible light and the rest is infrared and ultraviolet. This is a much more "useful" percentage. I'm not sure what the percentages are for LED, but does it really matter? If the percentage is low then all that means is that you need more LEDs to do the job and that you'll pay a little more for the electricity. If the percentage is high you'll just have to be more careful not to use too many otherwise you'll have algae problems.

Lord_Lucan said:
I would have thought a 200lph filter combined with an additional pump would be adequate circulation but then again I could be talikng rubbish. The feedback I am getting is that there is a massive difference in succesfully achieving a 30" tall set up against a 24" set up, would you say this is the case?
Well there are two issues involved here. The first is to have adequate flow rate, which I assume you do based on the 10X rule, but the second factor is how the flow is distributed and how effectively the CO2 is dissolved. Distribution is very tricky because inattention to flow patterns can easily result in stagnation points and destructive interference. The energy of the pumps must be translated to a certain velocity across the surface of the leaf. The CO2 must be dissolved within that mass velocity in order to be transported to the leaf surface.

It's easier to do this in 24 inches than it is in 30 inches simply because the inertial forces acting against the transportation of a unit mass of water across these distances are more prohibitive as the distances increase.

On the other hand light energy dissipation typically follows the inverse square law, so that the energy loss is quadrupled if the distance from the bulb is doubled. The light falloff difference from 24 inches to 30 inches is about 60% which sounds like a lot, but all the plant has to do is produce more chlorophyll and to pack them more densely per square centimeter. So plants at 24 inches are less efficient food producers than plants sitting at 30 inches. Making extra chlorophyll is easy for plants but making more Rubisco to capture more CO2 is a lot harder. Ironically, if flow to the substrate is poor, it actually helps the plant that there is less light.

So when people experience failure with deep tanks they typically blame it on poor light penetration, when actually it's almost always due to poor CO2 penetration. I appreciate that the monetary outlay for the lighting is significant and that you want to make the right choice, but the only thing you have to worry about is to not exceed the energy levels. You don't have to worry about what color or what suitability. You can get bulbs to suit your taste. This is never an issue. It is excessive light energy levels combined with poor CO2 injection techniques and poorly designed flow distribution that result in deteriorated plant health and subsequent algal blooms.

If CO2 and flow distribution is well implemented, the only penalty of the light falloff for a 30 inch tank is that growth rates will be slower than if it was 24 inches. The health of the plants however will be excellent.

Cheers,
 
Mr Lord Lucan (?),

if you wish to look at my own thread on ~1600 litre aquarium. It is 28" high and 36" wide, 96" long. I have 432watt system over the entire tank, but actually only need 216 watts of lighting (the lighting units are at least 15" above the water surface). These were T5 Powermodules. 216 watts gives me a PAR reading ranging from 25-40 at the substrate which has been enough to grow the likes of hairgrass. It would be more ideal to have a uniform lighting at the susbtrate of 30-40. If i have all lights on (432) I get more like 40-60 PAR (if i remember correctly), but then at the surface this rises to >200.

Essentially I would keep lighting as the limiting facotor and the other nutrients in excess (if you are doing EI), that way you can better control the system.
 
Back
Top