Lighting Question (WPG vs Lumens)

[darkdep]

In researching lighting, I've discovered that many people rate the "proper amount of lighting" for various planted setups in WPG (Watts per Gallon).

This doesn't make sense to me (because I'm probably missing something);

- an old style T12 flourescent produces a certain amount of light (lumens) utilizing 40watts of electricity

- A newer T8 produces roughly the same amount of light, but only uses 34watts of electricity

- A Power Compact / T5 bulb is even more efficient, producing a larger amount of light per watt.

It seems to me that WPG is a strange way to rate light output, as different bulbs produce different light per watt. Because of this, I'm having a hard time figuring out how much light I need.

Can anyone comment on this, so I don't feel so dumb?

[Marc]

I'm not an expert but I think that it's safe to assume that the WPG guidelines apply to the old style T12 bulbs and would then need to be adjusted for whichever bulb you are actually considering.

Marc

[darkdep]

I guess I'm trying to figure out if a 96w power compact bulb with a good reflector is enough light for a moderately planted 90gal X=)

[BigDaddy]

The true measurement you are looking for is PAR (photosynthetically available radiation).

And its not a question of how heavily planted the tank is, its a question of the light requirements of the tank.

If you plant nothing but Java ferns and anubias, etc... then sure, the 96 watt is perfect.

But I would suspect with a "tall" 90 gallon (24 inches high), your will not be able to get light to the bottom of the tank (so forget carpetting plants), and even medium light requirement plants will likely suffer.

The difference between a 34 watt T8 and a 40 watt T12, as far as plant growth is concerned... is negligible.

[TBarb]

...
The difference between a 34 watt T8 and a 40 watt T12, as far as plant growth is concerned... is negligible.

Therefore I would go with the T8 34 watt bulbs (as I did) Electricity is expensive enough as it is.

I would be interested in the efficiency of say a regular NO T8 setup vs Power Compact at the same wattage? - Any thoughts BigD?

[BigDaddy]

Well, compacts are basically twin T5 units.

It's kind comparing apples to oranges, mostly because in tube lengths, CF bubls are much higher wattage than NO bulbs.

If we are talking about 4 foot lengths.... well you have your t8 32 watt.... or you can put 2 24 inch 55 watt compacts.

110 watts compared to 32 watts in the same amount of space.  More heat, a little more electricity... but a lot happier plants.

Using similar sized tubing, think of it this way:

18 inch NO bulb = 15 watts
17 inch CF bubl = 36 watts

Which do you think your plants would prefer?   :lol:

[TBarb]

Well, compacts are basically twin T5 units.

It's kind comparing apples to oranges, mostly because in tube lengths, CF bubls are much higher wattage than NO bulbs.

If we are talking about 4 foot lengths.... well you have your t8 32 watt.... or you can put 2 24 inch 55 watt compacts.

110 watts compared to 32 watts in the same amount of space.  More heat, a little more electricity... but a lot happier plants.

Using similar sized tubing, think of it this way:

18 inch NO bulb = 15 watts
17 inch CF bubl = 36 watts

Which do you think your plants would prefer?   :lol:

What do you mean "basically twin T5 units". I agree that my plants prefer the 36watt over the 15 watt but if you compare watt for watt (regardless how much space they take up) which one outperforms?

I recently went from T12's to T8's. The lumen output is almost the same if not more (depending upon the bulb type) so my thought is that the T8 is more efficient. (Visually, it was more brighter but that may because the T12's were 6months old and were due to be replaced) So, can that same idea be used for the Power Compacts?

Thanks BigD.

[BigDaddy]

If you take a 4 foot T5 bulb and fold it in half ... you have a 2 foot 55/65W CF bulb (very basic but you get the idea).

CFs produce more lumens per watt than NO tubes do.

[kennyman]

i have a quote here from a decent aquarium book that may help to make the leap to lumens.

"As a rough guide, a standard rectangular, planted aquarium will require around 30-50 lumens per liter of water". As BigDaddy pointed out a tank full of Java Fern would do ok at 30 lumens/L. 50 would give you much grater abillites and performance.

Par is linked prety much to the K valu of heat the light is using. It is can be compared to the radiation spectum so you can get  an idea of what type of energy your puting into your tank. Light is afterall just radiation.

http://saltaquarium.about.com/cs/lighting/l/aa031300f.htm

[BigDaddy]

Par is linked prety much to the K valu of heat the light is using. It is can be compared to the radiation spectum so you can get  an idea of what type of energy your puting into your tank. Light is afterall just radiation.

Not exactly.  You can have two bulbs with the same Kelvin rating, and yet have very different PAR values.

The easy definition of Par is this.  Lux measures the amount of light on a given area that a human can see... PAR is the amount of light per second (yes PAR has a time reference) a plant can use for photosynthesis.

[TBarb]

So how do you find the PAR value of a certain bulb?

[BigDaddy]

With a quantum sensor.

You won't find a bulbs PAR value on the bulb or retail marketing.  You probably won't even find it on the manufacturer's web site.

Getting back on topic with darkdep's question, it really boils down to this:

WPG is a good beginner's rule using ANY fluorescent bulb.  Essentially, stick to the guidelines of around 2 to 2.5 WPG for most low to medium light plants and you'll do okay.

[darkdep]

At this point I'm thinking of building a T5 setup.  Seems like Aquaria Canada has all the parts I'd need...

- Workhorse 7 Ballast
- Waterproof Icecap T5 endcaps and standoffs
- 2 x 47" T5 Icecap Reflector
- 2 x Arc T5 10000k 54w bulbs

That list look ok?  I'll start with that setup and will add more if desired.

[BigDaddy]

Yup... you'll do low light plants just fine in that setup.  A few stem plants like hygro and hornwort would probably do okay as well.

Honestly, though.... two dual 48 inch shop lights would be a cheaper alternative and give you as good or better results.  Not much of an upgrade path though.

Now... if you went with 4 of those T5 bulbs... that's another story.

[darkdep]

Wouldn't the 2x54w T5's produce better intensity than 4x32w T8?

[gvv]

Just to clearify - I though that wattage on the lamps is actually "how much electricity they will suck" to produce the desired lumens, that also shown on some lamps. And that Lumens (candelas, etc) are used for "luminous intensity" measuring.
So, from here WPG is just dealing with electricity bill...

[darkdep]

Well, yes!  See, I'm a bit of a tree hugger...I am trying to produce the most light per watt I can.

[BigDaddy]

Wouldn't the 2x54w T5's produce better intensity than 4x32w T8?

I've got the Philips catalog in front of me.

A 54W T5 produces 4750 lumen

A 32W T8 produces 1860 lumen (the T8 Alto series since we are talking about energy effeciency).

2 x 54 W - approx. 10000 lumen
4 x 32 W - approx. 7500 lumen

So, your looking at a 25% increase in light output.  Now the cost difference is substantial.  The T5 setup from Aquaria Canada is going to run you around $150 for ballast, bulbs and reflector.  Two shop lights from CT are on sale at $20 bucks each.  Plus, the T5 bulbs are significantly more expensive than the very cost effective F32T8s.  Given that you want to change bulbs at least once a year.....

If you are in it for the long term... and will probably go with higher lighting in the future, the T5 is a good long term investment.

If you just want to get your feet wet with plants and see if you catch the bug, I'd start with the shop lights first.

And I'll revise my previous comment.  "Results as good or better".... probably not better.  Didn't realize the output was as high as 25% better on the T5s.

[TBarb]

Another question regarding 'intensity' of lighting... For photosynthesis to occur, the plant will take in light that we don't even see with our eyes? So, a very lit tank means you 'see' a lot of light. Some light bulbs don't seem very bright (intense) but they do give off (radiate) a lot of unseen light?

Comments

Welcome to science class 101

[BigDaddy]

Another question regarding 'intensity' of lighting... For photosynthesis to occur, the plant will take in light that we don't even see with our eyes? So, a very lit tank means you 'see' a lot of light. Some light bulbs don't seem very bright (intense) but they do give off (radiate) a lot of unseen light?

Comments

Welcome to science class 101

I don't doubt that the Philips "Aquarium & Plant" bulbs probably do have a PAR value that might be equal to a similarly sized daylight bulb.... but frankly, they just make the tank look dark and depressing!

Actually, checking with references again a Gro-lux 40 watter has a PAR rating of 41.2 uE/s.  A Daylight Deluxe 40 watter has 42.3.  So, the Daylight Deluxe not only generates a higher PAR value, it also makes the tank "look" brighter.  In fact, the Philips "Natural Sunshine" 5,000K bulb has a CRI of 92!  That's excellent color rendering.  So you get good PAR and very good coloring without using those pink "plant" bulbs.