# too much light?



## travdawg (Mar 3, 2005)

I just got my new tank, & I went ahead & ordered my light for it. The tank is a bowfront & used... I believe its a 46 gallon Oceanic, which is 16-18" high. I wanted to clock in right around 2 WPG, so I picked up a 36" 96watt PC light by Coralife. I was told last night by a fellow hobbyist that this light, being PC would actually clock me in at a higher WPG... This has me concerned that I am going to end up with much more light than I need to have a low maint, el natural tank... Can anyone advise me if they have any experience with something like this??? I dont want an algae farm!!! Do I need to return the light for something lower? I hate to return it, but like I said, I dont want to end up being closer to 3 wpg, than 2.


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## cs_gardener (Apr 28, 2006)

Normally when talking about wpg it's CF that's the standard, not regular fluorescent bulbs so you do have about 2 wpg. The Coralife reflectors are okay but not exceptional so they won't increase the light the tank receives by all that much. 

Since you're doing an NPT will the tank be getting sunlight? An NPT tank really isn't a low light tank as sunlight is much stronger than even CF bulbs and if your tank isn't getting any sunlight you need to make up for that lack. Even a couple hours of sunlight (even bright indirect light) in the morning or evening makes a huge difference in what will grow and how well everything grows.

Also, will you be using floaters? Both surface floaters and water column floaters can block a lot of light and they take up a lot of nutrients that will cause algae. So if you have floaters you can regulate how much light gets to the rest of the tank by how much surface area you let the floaters cover.

If you decide to keep the light you will need to be careful at the outset because the plants will be stressed and adjusting to the new conditions which is a prime time for algae to take hold. Having a lot of easy fast growing plants from the start will help immensely. There are always some algae problems that show up but they usually pass pretty quickly as the plants get established.

Most of my tanks aren't pure El Natural as I dose low levels of gluteraldehyde (generic Excel) daily to give the plants a bit of extra carbon. I don't dose anything else and algae is minimal, it's there but I can live with it. My tanks include 20 gallon tall w/65w CF, 33 gallon with 2x65w CF, and a 29 with 65w CF smack in front of a southern window thats so bright it makes it look like the light isn't on even when it is.  General care is dosing the excel, feeding the fish, trimming stem plants every 2-4 weeks, scooping out excess floaters every 1-2 weeks, cleaning the filter every 3 weeks or so for a quick filter, much longer for the tanks I've converted to canister filters (I like having less equipment in the tank - more room for plants!), and a WC every few months.

So where am I going with this? Yes, you can make your light work and you can grow about anything you'd like and it doesn't have to be a lot of work. If you want to go really low tech and don't mind having limited plant choices you could get less light and focus on the really easy to grow plants like crypts, anubias and ferns. I've done this in my 44 gallon tank with 65w CF. I do virtually nothing with the tank (I dose the gluteraldehyde, feed my fish, remove overgrown plants every 2-3 months, and scoop out floaters every week or two, do the same filter cleaning & WC as above), but I'm very limited in the plants I can grow in it. It all depends on what you're after and what you consider low maint.

edit: sorry for blabbing on and on. I didn't realize how long my post was 'til I posted it.


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## travdawg (Mar 3, 2005)

Thanks for the detailed response!!! No need to apologize for blabbering, I really appreciate the person experience & information. 

My plans for my tank are to stock heavily... as far as plants, I have not decided entirely... I am looking primarily for slow growers that are easy to trim. A couple of years ago I had a tank that was under high light & pressurized co2, I was in the tank twice a week pulling out tons of weeds. I do plan on utilizing some floaters, likely something like Hornwort, since it grows super fast & not quite as muhc of a pita to get rid of as duckweed. The tank will not be in direct sunlight ever.. so I plan on an extended photoperiod (if I read the info on here correctly, thats the proper thing to do). I am not using any filtration other than the JBJ Submariner for UVS & a little bit of water movement. No heat to start with either, I am going to see how the tank does at room temp.

I may switch to a HOB of some kind if I need carbon, or something is lacking.. but my hope is that this will be all I need to pickup! If you have anything else to add, please dont hesitate... I am hungry for more info!


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## dwalstad (Apr 14, 2006)

travdawg said:


> Thanks for the detailed response!!! No need to apologize for blabbering, I really appreciate the person experience & information.
> 
> My plans for my tank are to stock heavily... as far as plants, I have not decided entirely... I am looking primarily for slow growers that are easy to trim. A couple of years ago I had a tank that was under high light & pressurized co2, I was in the tank twice a week pulling out tons of weeds. I do plan on utilizing some floaters, likely something like Hornwort, since it grows super fast & not quite as muhc of a pita to get rid of as duckweed. The tank will not be in direct sunlight ever.. so I plan on an extended photoperiod (if I read the info on here correctly, thats the proper thing to do). I am not using any filtration other than the JBJ Submariner for UVS & a little bit of water movement. No heat to start with either, I am going to see how the tank does at room temp.
> 
> I may switch to a HOB of some kind if I need carbon, or something is lacking.. but my hope is that this will be all I need to pickup! If you have anything else to add, please dont hesitate... I am hungry for more info!


It sounds like you're on the right track. I like it that you have a UV sterilizer. Hopefully, fish diseases and green water algae in your tank will be lessened by this choice.

One minor point: Hornwort is a rootless, but submerged plants. Although, it does come near the surface, it is not a "floater" and will not help you out in terms of algae control and light reduction.

True floating plants (Duckweed, Frogbit, Azolla, Water Sprite, Water Hyacinth, etc) are exposed to the air. They have the 'Aerial Advantage' (Chapter IX in my book). Because these plants access air CO2 and light, they have an enormous advantage over algae. They grow much faster, take up nutrients faster, etc, etc than submerged plants.

If you have 96 watts PC light over a 46 gal tank, floating plants will be a big help in controlling algae. The floating plants I like are Frogbit and Water Sprite. They're easy to remove-- and not bad to look at I might add.

Make sure that the temperature in your tank without a heater doesn't get below 72F.

Folks, please remember this simple fact: Any plant foliage that comes in contact with air is emergent growth and has the aerial advantage. Hornwoth doesn't qualify.


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## aquabillpers (Apr 13, 2006)

cs_gardener said:


> Normally when talking about wpg it's CF that's the standard, not regular fluorescent bulbs so you do have about 2 wpg. The Coralife reflectors are okay but not exceptional so they won't increase the light the tank receives by all that much.


The "old" rule of 2 WPG of T12 fluorescent light energy as the maximum for a low light aquarium is still valid. CF produces more light energy per watt, so one would need fewer watts to obtain the same effect. Trav has too much light and he should take remedial action, as has been suggested here.

Here is a link to a discussion between Tom Barr and me about the differences between the various kinds of lighting.

http://www.barrreport.com/general-plant-topics/3281-lighting-comparisons.html?highlight=light

Bill


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## ruki (Jul 4, 2006)

aquabillpers said:


> The "old" rule of 2 WPG of T12 fluorescent light energy as the maximum for a low light aquarium is still valid. CF produces more light energy per watt, so one would need fewer watts to obtain the same effect. Trav has too much light and he should take remedial action, as has been suggested here.


Wow, a lighting discussion in the El Natural forum.

(1) WPG?
I don't think that WPG was something that was ever understood. I think it gave a people a false understanding that an oversimplified model was some sort of absolute rule to follow instead of a rough estimate. To make the number a better estimate, one need to adjust for tube technology, reflector efficiency, depth of the tank, age of the tubes, temperature the tubes are at and how much of the light produced is useful to plants. This will add +300%/-80 percent to the raw WPG number. (Repeat after me, WPG is a rough estimate, not a rule.) 

In some situations, 2 watts/gallon CF will work for a low-light tank. For example, I have the horrendously inefficient Coralife 98 watt "quad tube" CF fixture, it's the one with the tube bent back against itself three times which makes the reflector mostly irrelevant. I have it on a 15 tall, so that works out to 98/15=6.53 watts per gallon. The plants grow as if they are in a low-to-medium light tank. Put this 98 watt light over a 50 gallon tank and you will have low light tank, if that. I admit this is a worst case scenario for WPG, but as long as I am taking shots at it. :lol:

(2) CF is OK in terms of light output, but there are limits on how much can get sent down into the tank by the reflector. CF is similar to T5 HO, but it's less standardized and data on exactly how much light is produced by proprietary fixtures and tubes are not easy to find. When comparing these tubes for human eyes light, I remember:

T5 NO = 104 lumens per watt, most efficient at 35C?, tubes last ? months
T5 HO = 92 lumens per watt, most efficient at 35C, tubes last 18-24 months
T8 = 80 to 95 lumens per watt, most efficient at 25C, tubes last 6-12 months
T12 = 60 to 80 lumens per watt, most efficient at 25C, tubes last 6-12 months
CF = 60 to 90? lumens per watt, most efficient at ??C, tubes last 12? months

(of course lumens is light for human eyes, not necessarily light useful for plants, but one can compare light output across different tube technologies with it.)

(3) Reflectors make a huge difference. The narrower the tube, the closer one can get to the theoretical parabolic reflector with a point light source. Bent tubes (CF) wreak havoc with reflectors, so even though they might put out around the same efficiency as T5 HO, they shine light back at them selves across the tube bend and their extra runs block more light from the reflector.

But enough negativity on my part. :lol:

Gut feel is that the actual setup, 46 gallon 16-18" high Oceanic with a 36" 96watt Coralife PC light by Coralife should work out OK. If it turns out to be a bit on the bright side, just add some controllable floating plants (Giant duckweed, Salvinia natans, ...) as cs_gardener recommended. This will really clean up your water for any fish in the tank. It's really a good thing to have a bit too much light so you can use floating plants as nice filter. Then just scoop some out each week which is a defacto method of removing excess nitrogen in the tank.


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## aquabillpers (Apr 13, 2006)

The term "WPG" has many drawbacks, because of the several other variables that affect the amount of light energy that reaches the plants where is is needed. These were well summarized in the preceding post. The only reason that it is still being used is because it is a convenient way of estimating the amount of light that goes into a tank.

To me, a better term would be "lux". This is a measurement of the light energy that is actually delivered to a point, as opposed to "watts" which refers to the energy a lamp uses, and "lumens", which refers to the light generated by the lamp but not necessarily delivered to where it is needed. For example, a screw-in, spiral "CF" lamp might produce the same lumens as a certain fluorescent tube but but the actual delivered light will be significantly less, because of the shape of the lamp and "re-strike.".

Using duckweed and similar plants to reduce the amount of light works well. However, given the growth rate of duckweed, it can be hard to control the amount of light from day to day, and a stable environment is what we strive for in our NPT's. Another problem with duckweed is that it consumes a lot of nutrients, and shortages can develop to the detriment of the other plants.

Bill


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## ruki (Jul 4, 2006)

For sure. Actual measurements are better. Lux meters are relatively cheap. PAR would be better, but meters are quite expensive.

I agree that floating plants are not really appropriate for a high light show tank. I use them for medium light tanks where I don't have to change the water or sometimes even run a filter. Spirodella polyrhiza, Salvinia minima, and Salvinia natans do a good job. The fish produce the Nitrogen and I add micros each week. It's fun to break the "you must do water changes" rule. Ameca splendens and some other live bearers thrive in such tanks. They also tend to clean up the algae too. These are quite minimum maintenance tanks.


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