# Watts per gallon



## Regenesis

Haha. It gets me too. Ah well, they'll learn.


----------



## Sethjohnson30

Damn I set my tank up according that perhaps ou could shed some light on my situation( no pun intended) I have a 72g bow front with a 4x54w 48" fixture 7" above the tank, w/ glass tops I leave them on for 12 hours how am I doing. I have no idea what to go by now? I also have pressurized c02 and I use sea chem flourish weekly. Its been set up for two weeks now and I'm getting a lot I green algae but on the bright side all of my plants are pearling


----------



## Rane

Yes, I feel victim to this. Ended up buying waaay more light than necessary before being set straight by this forum.

The difficult thing is that there seems to really be no rule to go by. Nor even any clues in some cases. Watts are irreverent, lumens unreliable and often inaccurate, par readings rarely available, and everything changes from fixture to fixture even with similar technology.

Confusing, to say the least. I still don't quite have a grip on all of it. :confused1:


----------



## samamorgan

Sethjohnson30 said:


> Damn I set my tank up according that perhaps ou could shed some light on my situation( no pun intended) I have a 72g bow front with a 4x54w 48" fixture 7" above the tank, w/ glass tops I leave them on for 12 hours how am I doing. I have no idea what to go by now? I also have pressurized c02 and I use sea chem flourish weekly. Its been set up for two weeks now and I'm getting a lot I green algae but on the bright side all of my plants are pearling


Pull the two center bulbs out and your algae should come under control.

I would love for this post or a post like it to become a sticky. This is such a problem and leads so many people astray because it gets recycled over and over. I could certainly do a detailed write-up of why this isn't true, but the information is already out there about this issue for those who look.

PAR is the only standard that we can use right now, and even that is just a very close approximation. But at least it actually _applies_. PAR readings are readily available too. Between hoppy's research and my own LED compilation, those are two light mediums completely (almost) covered.


----------



## jkan0228

Sethjohnson30 said:


> Damn I set my tank up according that perhaps ou could shed some light on my situation( no pun intended) I have a 72g bow front with a 4x54w 48" fixture 7" above the tank, w/ glass tops I leave them on for 12 hours how am I doing. I have no idea what to go by now? I also have pressurized c02 and I use sea chem flourish weekly. Its been set up for two weeks now and I'm getting a lot I green algae but on the bright side all of my plants are pearling


Just a general reference
http://www.plantedtank.net/forums/lighting/105774-par-vs-distance-t5-t12-pc.html

I say general because each and every setup is original and one of its own.

Where in Portland are you located??


----------



## plantbrain

samamorgan said:


> Thank god this isn't a political forum, i'd go nuts.


Plant Politics, sorry, everything is political:hihi:

An Apogee light meter for your local club is a good idea, then folks can borrow or rent it out since it's somethign folk's might use once a few times and then only when they get a new tank.

This way you can measure plants, any and everywhere, light fixtures, make your own curves, estimate the light a plant receives as it grows up towards the light etc.

Takes out all the other factors involved and reduces it to the unique tank.
I see folks hollering about the need to measure and dose carefully, less is best, then they give light a blank check.

Or worse........CO2..........

Put another way, "a good myth is hard to kill."


----------



## samamorgan

I'm just going to start pointing people to this post every time i see someone say anything about watts per gallon. A sort of "here's your sign" deal.


----------



## Sethjohnson30

jkan0228 said:


> Just a general reference
> http://www.plantedtank.net/forums/lighting/105774-par-vs-distance-t5-t12-pc.html
> 
> I say general because each and every setup is original and one of its own.
> 
> Where in Portland are you located??


I'm in the foster Powell area


----------



## BBradbury

*Watts per Gallon*



samamorgan said:


> Just here to rant about a pet peeve. Stop talking about wpg!!! It doesn't apply do anything; it gets said over and over and corrected over and over. I cringe every time i see someone reference watts per gallon. Hell it really didn't apply to anything but the most basic setups "back in the day", and doesnt apply at all now. By keeping that awful rule of thumb in your head and spewing it out on these forums, you're further confusing new aquarists that come here to make informed decisions about lighting and further propagating an outdated and simply bad idea. *STOP SPEWING WPG RULES AT PEOPLE!!*
> 
> And that's my rant for today. I'm allowed one per week, right? Thank god this isn't a political forum, i'd go nuts.


Whoa, sam...

Watts per gallon works great for those of us "old timers" using only T8s and T12s to light out tanks. I've used the rule for close to 10 years and my planted tanks are a jungle.

I use the list below to light all my tanks:

Up to 1 watt of light per gallon of tank volume: Low
Up to 1.5 watts: Moderate
Up to 2 watts: Strong
Up to 3 watts: Bright
4 watts + : Very bright

Lighting a standard aquarium dosen't have to be "brain surgery". Heck, all you really need are 6500 K bulbs from the local hardware store and you're good. Hope this doesn't offend anyone, but if you stick to the basics, this eliminates all the lighting "brain damage".

Just a thought from an "old school" water keeper.

B


----------



## somewhatshocked

BBradbury: Consider a standard 26w 6500K CFL.

Over a 2.5gal tank that's, say, 12 inches tall? That's more than 10 WPG. Over a 20gal tank that's 12 inches tall? That's barely more than 1 WPG. In both situations, the amount of lighting hitting the substrate is probably the same.

You could add another 26w bulb to the 20gal and have 2.6 WPG and still have extremely high light with moderately decent reflectors. Over a 20gal tank that's 18 inches tall? You'd need maybe 3 or 4 of those bulbs to get the same light level, in my experience.

Could also have 150w of lighting hanging really high above a 2.5gal tank and still not have enough lighting to grow anything.

I think in your situation, you're using your experience and ability to discern proper lighting levels for what your plants need. Which is a terrific thing. It's not a matter of being an "old timer" or whether or not you use T5s or T8s. WPG just doesn't really apply in much of any situation, unfortunately. Way more than WPG is at play.


----------



## shortsboy

So you mean I shouldn't run 3 10w LED's over my 10g??? It's only 3 WPG.


/sarcasm


----------



## chicken

samamorgan said:


> *STOP SPEWING WPG RULES AT PEOPLE!!*
> 
> And that's my rant for today.


Feel better? :icon_smil

The watts per gallon "rule" reminds me of the inches of fish per gallon "rule" for tank stocking that people like to repeat. 

I think watts per gallon does not want to die because:

1. It's simple. 
2. It seems to work well enough in some situations. 

Back when everyone was using T-8 and T-12 lighting on standard size tanks, it appeared to work well enough. I suppose that was more of a coincidence than anything else. But somehow this "rule" got carved into stone. Except it didn't work for very small tanks. Or very large tanks. Or very deep tanks. Or --well, you get the idea. Funny thing is, even with all these "exceptions" it was still the "rule!" 

And then PC lighting became more common. And the fact that reflectors can make a big difference became more widely known. We still tried to use wpg, but kept adding to the list of "exceptions." And then there's metal halides. And then came T-5s, and now LEDs! There's no hiding from the fact that wpg truly means nothing at all now, and there doesn't seem to be any rule to replace it! This is the point at which I gave up hope of feeling like I could ever understand lighting at all! :confused1:

I really wish there were a formula as simple as wpg for understanding lighting. PAR data is helpful, but not widely available. What I have found most helpful is to find out what other people are using in their setups, and how it's working for them. It's not perfect, but it works well enough. :icon_smil


----------



## Hoppy

In the good old days, the biggest lighting problem was getting enough to grow plants. Today, the biggest lighting problem is getting a low enough intensity to grow plants instead of algae. Different eras, different problems, different "rules".


----------



## samamorgan

BBradbury said:


> Whoa, sam...
> 
> Watts per gallon works great for those of us "old timers" using only T8s and T12s to light out tanks. I've used the rule for close to 10 years and my planted tanks are a jungle.
> 
> I use the list below to light all my tanks:
> 
> Up to 1 watt of light per gallon of tank volume: Low
> Up to 1.5 watts: Moderate
> Up to 2 watts: Strong
> Up to 3 watts: Bright
> 4 watts + : Very bright
> 
> Lighting a standard aquarium dosen't have to be "brain surgery". Heck, all you really need are 6500 K bulbs from the local hardware store and you're good. Hope this doesn't offend anyone, but if you stick to the basics, this eliminates all the lighting "brain damage".
> 
> Just a thought from an "old school" water keeper.
> 
> B


I understand where you're coming from, and that completely makes sense. I can probably give you something pretty close in terms of watts per gallon when it comes to LEDs as well. But that's because I have experience with them and know the PAR values and outcomes behind a ton of different situations using about 15 different emmiters.

somewhatshocked hit it on the head really, i think your usage of the rule really comes down to your experience with the fixture. It has worked for you because you've used the same tried and true method over and over and can reasonably predict your outcome based on past experience and similar situations you've seen. But this idea given to someone with zero knowledge on the subject is much more of a hindrance than help. It starts people off on this idea that is completely false in almost every situation and without that past experience to guide them many people easily get 5 to 6 times more lighting than they need. This leads to massive headaches and a terrible experience for the new aquarist which might possibly shy them away from the hobby. Sound advice leads to enjoyment.

When it boils down to it, i love this hobby. I spend way too much time, money, and energy on it. I want new people to enjoy it too, and not have to go through as many hoops as i had to go through when i started, if possible. It's the human condition to build upon the experiences of past generations.


----------



## Daximus

I don't have an issue with this really. Certainly if there was a better, more available means of measuring the light I'd be all for it. But there is not. Watts per gallon is a good place to start the conversation. 

Much like "one inch of fish per gallon" isn't a real good way to judge capacity, it starts the conversation. There are too many variables for *any* rule in this hobby if you ask me. 

I guess my point is if people don't think in terms of w/p/g, then in what terms should the discussion be started? If anything, the "rule" just needs to be updated a bit for the inclusion of T5s and the like. 

Even in the T8 hay day, when the "rule" was somewhat useful, elevating a light would effect it's potential. So I think we would all agree it's a given the w/p/g references standard "light on tank" (not elevated) situations. Again, back to referencing the T8 hay day, I would assume some fixtures were of better quality than others, thus effecting the potential strength of the light. 

The issue is, it's not a "rule" it's a guideline. Rules are hard and fast, guidelines have some room for variation and/or deviation. 

If we all a way to easily measure PAR or PUR then I would agree that the w/p/g "rule" is irrelevant. We don't, so I would rather update the "rule" (guideline) to something more relevant given the inclusion of today's lights. 

For instance... (and only as an example)

T8 reference:

0-1.5 w/p/g low light, more or less
1.5-2.5 w/p/g low-medium light, more or less
2.5-3.5 w/p/g medium, more or less
3.5-4 w/p/g medium-high, more or less
> 4 w/p/g high, more or less

T5 reference:

0-.5 w/p/g low light, more or less
.5-1 w/p/g low-medium light, more or less
1-1.5 w/p/g medium, more or less
1.5-2 w/p/g medium-high, more or less
> 2 w/p/g high, more or less

The above not being a rule by any means, but a decent conversation starter. Tank height, quality of lights/reflectors, light elevation, potential foliage cover...etc., will always be a consideration until each of us has a PAR meter. 2 cents...

I think the bigger task at hand in the hobby is to get people out of the mindset that they need half as much light as they think they need. I'm not sure if it is the T5HO craze, or the abundance and low cost of powerful marine light setups, or merely the lack of market saturation when it comes to planted tank light fixtures...but it's crazy. My taller plants pearl daily (with Co2 of course) in my 90 gallon running a paltry (by today's standards) 1.42 w/p/g of T8 light in fixtures with very questionable reflective properties. I've joked about it in the past, but I'm getting into the habit of telling new people to buy 1/2 the light they think they want, lol.


----------



## houseofcards

To date I have not found one reliable way to know if you have the 'right' amount of light. There are just too many variables as Daximus alluded to. A light meter will let you know how much light there is, but depending on tank conditions, etc. it's still not full proof IMO. Light meters also will not be in the hands of most newbies who need it most (unless it becomes or should I say when it becomes an app).

Experience and experimenting is still key.


----------



## Wasserpest

samamorgan said:


> I would love for this post or a post like it to become a sticky. This is such a problem and leads so many people astray because it gets recycled over and over. I could certainly do a detailed write-up of why this isn't true, but the information is already out there about this issue for those who look.


Really? You post a rant, and then want it to become sticky? You think your post is so valuable that everyone needs to read it?

How about something a bit more constructive? Rather than yelling ("STOP SPEWING WPG RULES AT PEOPLE!!") offer a simple solution perhaps?

Isn't the real issue that someone blindly follows some arbitrarily set value ("3wpg!!") without adjusting for more efficient, brighter bulbs and better reflectors available today? We all know that hardly anyone is using T12 bulbs today, and likewise, know that the wpg numbers of the old days don't apply anymore. They are not set in stone, you know?



samamorgan said:


> *PAR is the only standard that we can use right now*, and even that is just a very close approximation. But at least it actually _applies_. PAR readings are readily available too. Between hoppy's research and my own LED compilation, those are two light mediums completely (almost) covered.


You have very strong opinions. While there is certainly some truth in that the wpg formula is flawed, doesn't apply well to LEDs, etc, it is still a very useful approximation if adjusted for the type of bulbs, tank size, and whether and what kind of reflectors are used.

When planted tankers read the numbers off their bulbs and state they have 2 wpg over their 55gal tank that tells me quite a bit. Most likely a double T5HO fixture. Give me some more info, a brand name or reflector type and we are getting really close to being able to judge the light level, and to give some recommendations based on that.

Now someone else pulls out their PAR meter (wait...) and finds that there are 17.3 micromols (per square meter) (per second) underneath that Nymphaea leaf, does that mean that they have "enough" light? Would that be a huge improvement? Let's see a show of hands... who all has a PAR meter?

Photosynthetic active radiation and photon flux area density and such sound all great, but most of us don't have the means to measure them, and declaring that "it is the only standard right now" will just frighten newcomers to the hobby. PAR measurements will give us a more exact picture, but you will continue to see Wpg numbers thrown around, and it would be wise to relax a bit and accept that. As PAR measurements are shared, they will become more topic of discussion when comparing setups, but you STILL will see "3W LED" and "28W T5" and a tank volume along with it. Bulbs/LEDs will still be sold by wattage, and we still want to know how big the tank is that needs to be illuminated.

Let's keep an open mind...


----------



## houseofcards

Sethjohnson30 said:


> Damn I set my tank up according that perhaps ou could shed some light on my situation( no pun intended) I have a 72g bow front with a 4x54w 48" fixture 7" above the tank, w/ glass tops I leave them on for 12 hours how am I doing. I have no idea what to go by now? I also have pressurized c02 and I use sea chem flourish weekly. Its been set up for two weeks now and I'm getting a lot I green algae but on the bright side all of my plants are pearling


This type of reaction is the problem IMO with a thread like this. Blaming your issues on WPG is very narrow-minded. There is plenty of information available on how to start up a tank and one of them is certainly not to run your lights for 12 hrs. In fact the majority of even mature tanks might have a problem with that duration. There is also a slew of other things that need to be done during the start up period to reduce the chances of problem algae.


----------



## thebileball

houseofcards said:


> This type of reaction is the problem IMO with a thread like this. Blaming your issues on WPG is very narrow-minded. There is plenty of information available on how to start up a tank and one of them is certainly not to run your lights for 12 hrs. In fact the majority of even mature tanks might have a problem with that duration. There is also a slew of other things that need to be done during the start up period to reduce the chances of problem algae.


i know im being lazy by asking you instead of searching my question. when you mention to not run your lights for 12 hours, it is because of algae growth right? also, if i have a flourescent running along with a 60 micro or nano? watt light, the led doesnt put out much light as far as photosynthesis is concerned, so if i ran the LED for 12 hours and the flourescent for maybe 8 would that have the same effect on algae growth? i would imagine not because the LED isnt putting out as much energy?


----------

