# Dispelling the myth on light levels



## tsunami

Before power compact lighting was available, people on APD created a sort of watts per gallon guideline to serve as a rule of thumb for planted aquaria:

below 2 wpg ---> low light
2-3 wpg ---> moderate light
3-4 wpg ---> high light

This guideline was created at a time when normal output flourescents with white paint as a reflector were the norm. Somehow, this watts per gallon rule stuck in the planted aquarium hobby despite considerably advances in lighting technology. Many newcomers to the hobby believe that they need 3 or more wpg to grow a wide variety of plants --and this is not true, especially when they are referring to 3 wpg of power compact lighting with good reflectors (such as AH supply's). I believe that hobbyists in the US, as a result of continuing to apply these rules to power compacts and VHOs, use considerably more light than many other foreign hobbyists with equally successful aquariums.

My experiences: 

I started out with 2x55w power compact lights from AH Supply. On my 55g, they provided exactly 2 wpg according to the rule as a recommendation from Erik Leung. He told me I could grow anything with that amount of lighting. He was right. During that time, I grew Rotala macrandra, Rotala wallichii, Heteranthera zosterifolia, and Alternanthera reineckii in very large quantities. The plants grew in large and lush. I was very pleased. When I tried Glossostigma elatinoides, again using his advice, I planted the runners horizonatally into the substrate. The Glossostigma grew as flat as any glosso foreground I had seen in books or on the net! 

During the first year that I was away at school, I left the tank with a single 1x96w power compact light on my 55g. I did not believe that anything would do well with such "dim" lighting levels. When I came back for winter break, I was astonished. The Bacopa caroliniana was large, robust, and pink. Hemianthus micranthemoides grew as a beautiful, compact mound (I wish I could get it to grow as well at higher light levels where the individual stems tend to become smaller and a little rattier). The grouping of Ludwigia repens grew as a beautiful large specimen taking over 1/3rd of the tank. After seeing this, I dared to try more species --Proserpinaca palustris, Didiplis diandra, Lysimachia nummularia, Alternanthera reineckii, Rotala wallichii. They all did very well and were as healthy as any plants I've had in my "high light" tanks.

There was one problem though. The dense growth at the middle and top layers kept shading the bottom so that nothing could prosper there. Solution: I planted the substrate with Cryptocoryne wendtii 'green', Anubias barteri v. nana, and Cryptocoryne wendtii 'red' to cover up the substrate and bare, leafless lower stems. They also did well in their respective places...

So, should the wpg be shifted downward to reflect the greater efficiency of aquarium lighting today? Should 4 wpg be recommended to newbies wanting to grow a large variety of "high light" plants? Should we start recommending 1.5 wpg to people who just want to grow crypts, ferns, and Anubias? Why or why not?

Carlos


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## shannon

Good stuff Carlos  

Did you use Co2? I'm assuming not. How was this tank fertilized? (while at school). What was your PH? Fish load? Hope you don't mind my questions. From your wonderful post it appears there is hope for those of us low tech / limmited income, but plant crazy individuals!!

Thank you much.... Shannon


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## tsunami

During that time, I did use CO2. I had a 2 liter DIY CO2 bottle running into a Plantguild reactor (efficient!). CO2 is simply too important for growing many of the more demanding plants --even though the light intensity they require may not be as high as most think. I've since switched completely to pressurized CO2 on both of my tanks (get this before getting good lights!).

My pH, as a result, was about 6.6-6.8 which would be about 25-30 ppm.

My fish load at the time was moderate (both times):

At 2 wpg
~2 discus, 2 peruvian altum angelfish, dozen cardinal tetras, 4 Corydoras sp, 5 Otocinclus, 3 Rummynose Tetras

At 1.75 wpg
~2 large Peruvian Altum Angelfish, 9 Cardinal Tetras, 5 Otocinclus,
3 Dwarf Gouramis, 4 Corydoras 

When I am away from school, my mom doses, prunes, changes the water of this tank. For this time around, I am keeping the lighting at 2.55 wpg. Ammania gracilis, Heteranthera zosterifolia, Ludwigia sp Cuba, and Limnophila sp Gigantaea are all doing well. I also have a lot of Anubias, Crypts, moss, and ferns in that tank right now.

From the interview with Oliver Knott, I realized that you really do not need very intense lighting to have a gorgeous planted aquarium (although you do need an efficient one... remember his T5 tubes are much more efficient than the standard T12). Also, he uses pressurized CO2 in all of his tanks, I believe. It makes a big difference in the health of your plants even if your aquarium does not have very intense lighting.

Carlos


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## plantbrain

So are you now a low light convert?

Regards, 
Tom Barr


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## Justin Fournier

Tom,

Low light is all one needs, it's slowwww, but sometimes speeding is FUNNNNN!!!!


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## tsunami

I agree with Justin full heartedly!  

Carlos


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## plantbrain

Well, my 6 watt a gal PC tank is not slouch
I've had one for 8 years now.

It's taught me a lot.

I think one thing that is often over looked with the comparisons of NO to PC: the spread of the light.

A 55 gal with 110w of PC lighting does not have the same angle and spread that a 4x40 NO light set up has.

I notice when I am careful tlo account for light spread with PC's, I get better results with less.

Those AH reflectors are quite narrow and focused.

I think overall, things are fun with lower light, less work and worry if you neglect, those nice aquascapes stay there longer.

I like to enjoy them rather than working to keep them up so much these days.

Maybe you all will go non CO2 later? Hehe.
It's fun and amazing too, I got a nice one.
It'll take me 6-12 months to get one the way I want, but it'll stay like that for years to come.

Regards, 
Tom Barr


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## psidriven

Tom,

I also have a high light tank at about 6 wpg (240 pc over a 40 gallon cube) and wanted your advice on adding nutrients. Read some of the other posts showing that extra Fe+ is needed but is there anything else? Currently using Flourish and Flourish Fe+ at 1 ml dosees twice a week. Plants doing alright but the glosso is not taking off like it once did. Have co2 at 1 bubble every 2 seconds.

Thanks in advance for any advice give and looking forward to adding to this board soon.

Tony


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## tsunami

I'm not Tom, but I can tell you that you are not dosing nearly enough Flourish and Flourish Iron...

I would start off by dosing 3 mL of Flourish and 3 mL of Flourish Iron *daily.* Personally, I would continue to dose more and more Flourish/Flourish Iron over the course of a couple months until I no longer see any improvement.

Are you dosing any nitrate or phosphate? That may be part of the reason why your glossostigma isn't growing anymore.

Carlos


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## psidriven

Flourish and Flourish iron are the only additives I am currently using. The tank currently houses over 20 caridanls and 20 pencilfish along with a 6 inch silver arrowana. I felt the daily feeding should provide enough NO2-3 and phosphate to preclude dosing. I'll give the increased Flourish and Flourish Iron dosing a try. Is there a guideline for what levels of nutrients should be in a high light tank? That way I can have a target level to shoot for.

Thanks
tony


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## gpodio

I think WPG is variable depending on proportions of your tank and type of lighting used. Tom points out what I feel is an extremely important issue, light spread. When choosing lighting today, I will only choose PCs if there will be more than one in parallel. For example, 3x32W T8 tubes over a 55 gallon tank work far better IMO than 2x55W PCs. The PCs may penetrate more initially but become shadowed quickly. The better distribution of using multiple lamps reduces shadowing and maintains better lighting even in the bottom of the tank.

Smaller tanks seem to require more WPG than larger tanks to grow the same plants in the same way. For example, 1WPG over large tanks (90+gal) will grow many plants, including the ones that most people feel require double that amount. A 10 gallon tank on the other hand doesn't do as well at 1WPG and the selection of plants becomes quite limited. So proportions also matter and I think should be taken into consideration when suggesting WPG to someone.

You talk about bulb technology and this is something that also needs to be considered. T12, T8, T5, CF, MH all have different efficiencies, not to mention the ballast used which can make a T8 easily outshine a CF for example. So there is a lot here too to consider as well when speaking of WPG.

I come from a low light background and have been playing with high lighting for the last 3 years or so. Not sure I can say which one is better, it all depends on the amount of time and resources you are willing to put into your tank. I love the care-free low light tank that only needs monthly or bi-monthly water changes allowing you to simply sit back and enjoy the tank. But I also enjoy the fast pace and extreme growth rate a high light tank can provide, but there are times when I wish it didn't require so much work. I think most aquascapers will prefer the faster growth so that they can cut and shape their tanks in reasonable time.

If you're willing to do the work, get a CO2 tank, keep a log and do plenty of trials to find that perfect balance. I feel success in a high light tank is easier to acchieve than a low light tank. If something goes wrong, you simply do a large water change and try again. In low light tanks, I feel substrate type and fertilization is more important and messing that up can lead to disasters. High light tanks can be managed with water column ferts, even though that is not my method of choice, it's obvious it works well. Low light tanks on the other hand do better with a mixture of fertilization IMO or substrate fertilization alone. Mess up your substrate and you have a looong weekend in front of you  

Further, a high light tank consumes more than it produces, therefore deficiencies are the more common issues and can easily be corrected and large water changes as Tom suggests avoid accumulations. The "perfect" low light tank instead is at a balance between what is produced by fish load and feeding and what is consumed by the plants. Finding that balance can at times be tricky, changes in this balance take time to effect the plants and therefore a lot more patience is required, including a lot less fiddling around with things. Some people want to see faster results and don't have the patience to let things settle and mature as they should in a low light tank.

But I agree that suggesting 4WPG to a newbie is over the top. If the person wants to put in the time, then 2WPG _with_ CO2 will produce wonderful results and allow a little more room for error. Once the person has mastered this they can easily choose any amount of lighting and find it far easier to keep it under control. This is what I started with, just under 2WPG with CO2, then 3, then 4 and for the last two weeks I have been running 10WPG MH which will soon be reduced back to 2 so I can concentrate on a new setup. I'm sure it would have taken me longer to iron out the initial problems had I started with a much stronger lighting setup than I did.

Giancarlo Podio


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## tsunami

Tony,

With over 6 wpg, your fish are probably not enough to supply your plants with enough nitrate and phosphate. I know my fish aren't enough. I would invest in a couple of test kits. The ones I use are Aquarium Pharmaceutical's Nitrate test kit and Seachem's Phosphate test kit.

You should aim for:
NO3: 5-10 ppm (lean), or 10-20 ppm (richer, faster growth but less intense red colors out of your plants)
PO4: 0.5-1ppm (good), but personally I prefer 1-2 ppm

In a 40g cube, I would start off by dosing 3 mL of Flourish and 3 mL of Flourish Iron _daily_ into your aquarium. Before you do that though, I would check your N and P levels to make sure they are okay.

Sources:
Home Depot carries KNO3 in the form of stump remover. Don't forget to read the ingredients. It should say Potassium nitrate only.

Local pharmacy should carry fleet enema for phosphate. Personally, I like to dose with KH2PO4. You can purchase this chemical from:

www.litemanu.com

I'm curious to know why you have a silver arowana in your aquarium. I hope you do realize that these fish can get several feet long and will devour all your smaller fish as they grow.

Carlos


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## psidriven

Carlos,
Thanks for the info. That was exactly what I was looking for. Hopefully the plants appreciate the effort and start to really fill out. I'll hopefully have some pictures worthy of posting.

I've keep arrowanas before and like the way that they make the smaller fish school tighter. Guess it is natural reaction to predators. I usually trade them in when the get too large. Never have a problem with them eating the other fish since I get them small and train them to eat pellets.


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## Justin Fournier

I guess I should mention, that my 75G has most of the lights turned off these days, and is 90% crypts. Not much time to play with it so I removed all the stems, replaced them with Crypts, and a couple Nymphea. I don't do many water changes, and dose by appearances. Over the past couple months I have no algae, so I guess I am doing something right. 

Between the saltwater tank and all the time at work and home renos, I have no time for the tank. Oh the weather is good so I am biking more too.

The lights are still above the tank though, just waiting for thier time to shine


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## dennis

SO what would you all consider 3wpg on a 10 gallon? High or moderate? I am using 2x15 watt NO florescent. 1x6700k and 1x45k(I tihnk. Its one of the eclipse bulbs.) It seems that with the smaller tank size that the wpg rules go out the window but I am not sure what to expect. I have nothing to compare it to. And how much flourish would you recomend and how often?


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## tsunami

With two NO Flos, I think 3 wpg on a 10 gallon is moderate to low light. With this amount of light, ~4-6 mL of Flourish should suffice. 

The most successful 'high light' tanks I have seen with normal flourescents use at least 3-4 NO Flo bulbs packed under the canopy for ~5 wpg.

Carlos


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## dennis

Interesting tsunami, you really are disspelling the myths aren't you? Thanks for the florish reccomendation. 4-6ml, that would be over the course of a week, between water changes yes? I guess that there is not really anything in flourish that is going to help algae much is there. It does not seem to have enough in the way of macro nutrients to cause an excess of any of them. thanks


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## Justin Fournier

Over the past year or so I have stopped thinking of things in WPG. If it makes sence, I no longer think of things in WPG, but I think of it as minimum intensity. Everything photosynthetic has a minimum of light it requires. That would be the minimum intensity. Then think of it as close to or far exceding minimum intensity. 

I mostly deal with reef tanks at work, so that is far more my norm. When people ask how much does that X need? I respond atleast Y amount of light. That could be 10WPG or 1/2WPG depending on the tank, but the tank size is inconsequnetial to the light at that point. That is a much better way to explain it to people, as there is no confusion. 

An example, A S. gigantica needs atleast a 250W MH to thrive, does not matter if you have 30G or 175G. 2 customers of mine have Blue S. gigantica, one has a 33G (7.5WPG) one has a 175G (2.8WPG), both have 250W MH, both have beautiful thriving, fish eating gigantica. Makes sence?


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## dennis

So I guess that in reality we don't really care about wpg but more like watts per x amount of area, or lumens per x amount of area. Maybe we should all start trying to figure it out thatway instead. For instance, a 10 gallon tank has 200 square inches of surcace area. If 4 wpg, or 40 watts, is considered high light then in that senerio you would want 1 watt for every 5 square inches. Hmmm.... I guess that needs some more thinking for my brain to comprehend.


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## tsunami

Each type of bulb is not made equally. 110 watts over a 55g with normal flourescents isn't the same as 110 watts over a 55g with power compact lights and AH Supply reflectors.

The watts per gallon rule also breaks down in tanks smaller than ~20gallons (which need more wpg) and in tanks larger than ~90g. A 180g tank may function wonderfully with only 2 wpg, but to get the same results in a 10g, you would need 4 wpg. Takashi Amano seems to have realized this at a very early stage. In Nature Aquarium World Book I, his smaller tanks had 5-8 wpg. His larger tanks however were more on the order of 1-2 wpg.

Carlos


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## dennis

Very true. I believe mabye it watts per gallon could possible be refined to intensity or lumens needed. The only problem wiht this is htat finding the intensity of most bulbs is a bit challenging especiaslly concerning NO florescents. An example of this is what Justin were talking about earlier. A 175 watt MH over a 20 gallon will grow just about anything under hte sun. 2x175MH over a 75 gal will do the same. THe thing to think about, or so it seems to me, is that a MH has good coverage for an area approx 2x2 feet. A 20 gal is 24 inches long, a 75 gallon is 48 inches. I think the relationship there is obvious. The use of a MH for htis example might me overkill but if you changed the wattage of the bulb the realtionship between tanks is the same. over the 20 gallon you have 8.75 wpg and over hte 75 you have 2.3. Of course you must factor in the distance above the water surface and all but you get the idea. I guess I ramble and maybe this really is not that important in the end. Eventually we will al know that you need a certain amount of light for each tank to achieve a specific goal. the wpg rule would be obsolete by then any way with advances in lighting technology.


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## hubbahubbahehe

i would like to add that light spread is very important. In my 40 gallon tank, with pc's, the lighting doesn't reach certain areas of the tank and a s a result, the stem plants there will rot. 

Tsunami, I'm curious to know how you placed those 2x55w lightS over the top? in the middle of the tank or in the front? i would like to know how you managed to get good light spread?

hubbabubba


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## Justin Fournier

It's all in the reflector


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## hubbahubbahehe

Justin, the ahsupply reflectors are quite narrow though at about 4 inches.....


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## Justin Fournier

Try bending the edges of them out to spread the light. They are kinda shaped light a flat bottomed V. Bend the sides out to make it more like \_/. That will help.


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## hubbahubbahehe

tsunami said:


> During that time, I did use CO2. I had a 2 liter DIY CO2 bottle running into a Plantguild reactor (efficient!). CO2 is simply too important for growing many of the more demanding plants --even though the light intensity they require may not be as high as most think. I've since switched completely to pressurized CO2 on both of my tanks (get this before getting good lights!).
> 
> My pH, as a result, was about 6.6-6.8 which would be about 25-30 ppm.
> 
> My fish load at the time was moderate (both times):
> 
> At 2 wpg
> ~2 discus, 2 peruvian altum angelfish, dozen cardinal tetras, 4 Corydoras sp, 5 Otocinclus, 3 Rummynose Tetras
> 
> At 1.75 wpg
> ~2 large Peruvian Altum Angelfish, 9 Cardinal Tetras, 5 Otocinclus,
> 3 Dwarf Gouramis, 4 Corydoras
> 
> When I am away from school, my mom doses, prunes, changes the water of this tank. For this time around, I am keeping the lighting at 2.55 wpg. Ammania gracilis, Heteranthera zosterifolia, Ludwigia sp Cuba, and Limnophila sp Gigantaea are all doing well. I also have a lot of Anubias, Crypts, moss, and ferns in that tank right now.
> 
> From the interview with Oliver Knott, I realized that you really do not need very intense lighting to have a gorgeous planted aquarium (although you do need an efficient one... remember his T5 tubes are much more efficient than the standard T12). Also, he uses pressurized CO2 in all of his tanks, I believe. It makes a big difference in the health of your plants even if your aquarium does not have very intense lighting.
> 
> Carlos


Carlos,

in your time in school, did you have co2? if so, was it pressurized or diy?

I'm going to school after the summer and i am leaving a tank here but my mom is not as knowledgeable as your mom. And it's doubtful she wants to replace my diy co2...


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## aquoi

3+wpg and trimming is all glosso need to carpet and spread wild. 6wpg will bring lots of problems of imbalance. With that high amount of light, CO2 needs to be high and nutrients as well. It becomes unstable and hard to control.


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## tsunami

I still am in school. :roll: 

DIY CO2 my freshmen year. She refreshed it all right, once a week. 

Second year, I went pressurized... mostly because I wanted to pop in all my extra lights over the summer.

My mom has never kept a planted aquarium before. Sometimes it looks great when I come back, sometimes it's hellish. Oh well. 

Carlos


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## hubbahubbahehe

plantbrain said:


> I think one thing that is often over looked with the comparisons of NO to PC: the spread of the light.
> 
> A 55 gal with 110w of PC lighting does not have the same angle and spread that a 4x40 NO light set up has.
> 
> I notice when I am careful tlo account for light spread with PC's, I get better results with less.
> 
> Those AH reflectors are quite narrow and focused.
> 
> Regards,
> Tom Barr


I am interested to know how you "account for light spread" or adjust in order to get the light spread in a 55 gallon. Say, a 55 gallon with 2 x 55w ahsupply kits.

would this work for a 20 gallon high with 1 x 55 watt ahsupply kit?


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## gpodio

If you already have 2x55w CF lights for a 55 gallon, all you can do is change the shape of the reflector to spread the light out more evenly. You could also raise the lights to provide a better spread. The idea here is to use more than a single bulb over any part of a tank, this is the best way to improve light spread.

3-4 32W T8 bulbs for example would be a better choice than 2x55W CFs for a 55 gallon tank.

Giancarlo Podio


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## defdac

dennis said:


> I believe mabye it watts per gallon could possible be refined to intensity or lumens needed.


Lumens is bad.

Lumens is weighted towards yellow-green light which looks bright to us humans, but as you know is reflected by plants.

The photooptic curve = Human sensitivity
The action spectrum = Plant sensitivity

http://www.aquabotanic.com/images/light_fig9.jpg

That's why very bright looking yellow bulbs with very high lumens (SunGlo) doesn't grow plants nearly as good as dim low lumens GroLux-bulbs.


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## plantbrain

None of the hobbyists do well with light measurement, so we use a back door, make sure everythign else is in excess relative to the light level.

All in all, measuring light is tough, even for scientist.

Most use micro moles of photon's/M^2/sec.

Lumens, foo candles etc are poor, f/stops on cameras are as well.......

For us, the w/gal rule has never yet failed from everything I've seen. Most of the failure is the CO2, nutrient issues

I think some smaller tanks do well with more light etc, this is namely do to the spread of the source light rather the need for more intensity and also explains why larger tanks need less since there is more scattering and better spread.



Regards, 
Tom Barr


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