Rio 125 - Trouble Fitting Lights and Reflectors and WPG issu

Discussion in 'Lighting' started by mjenner, 23 Feb 2009.

  1. mjenner

    mjenner Member

    Messages:
    111
    Location:
    Chessington, Surrey
    Hi Guys,

    I've already pondered this one in my journal but rather than getting into a big conversation there, I thought I should bring it where it belonged... the lighting section.

    I'm in the process of upgrading and restarting my Rio 125. My fiancee won't let me have a luminaire or an open-top tank in the lounge, so I upgraded the Juwel lighting bar instead to a High-Light version (saw a good deal online and thought it easier than starting a pre-marital dispute over getting a luminaire). It looks great in the tank, and a lot brighter than my original setup.

    However, if I take the WPG value of the T5 bar, it's lower (in theory) than my original T8 setup.

    125l = 33 US Gallons (roughly)

    Original Setup - T8 Lighting Bar with 2 Extra Piggy-Back Tubes

    4x T8 Light Bulbs = 72w

    2.18wpg, but it actually looks dimmer.

    T5 High-Lite Only

    T5 Juwel High-Lite = 48W

    So, that's 1.46wpg, so not good, but to the eye it looks brighter?

    Planned Setup - T5 Lighting Bar + 2x T8 Bulbs

    T5 Juwel High-Lite = 48w
    2xT8 Light Bulb = 36w

    2.55wpg, the desired level, but having trouble fitting this all in the tank? :(.

    As per many people in this section of the forum, I'm chasing an elusive 2+ WPG as I'd like a nice carpet of HC or glosso.

    With the two T5's alone and reflectors, it looks brighter than if I add the T8's in, this is because to add the T8's in I need to lift the reflector to get the T8 underneath, changing it's angle and I think getting a lot of the output of the T5 striking the T8 rather than the reflector and vice-versa.

    I can't mount it further away towards the front/back as the incredibly helpful brace is in the way :(.

    I've done a small cross-section diagram (not to scale) to illustrate my problem below if it helps:

    LightingCross-Section.jpg

    Note, the T5's alone work really well with the reflectors, they rotate round and the outer edges rest on the centre brace, they're not quite as flat as they appear in the diagram (they're the standard Arcadia T8 reflectors) but my drawing skills let me down a little :).

    Does anyone know of a way of shoe-horning in two T8's with the T5's, and do they know of any more compact but still efficient reflectors any ideas? I really want to get my plants soon but I don't want to watch them go leggy, die and fade away through lack of light? (CO2 shouldn't be an issue, I have pressurised CO2, a ceramic diffuser (still in the post) and 2 Koralia nanos for flow).

    Thanks in advance,

    Matt
     
  2. Ed Seeley

    Ed Seeley Member

    Messages:
    3,262
    Location:
    Nottingham
    I've got Glosso, HC and Hairgrass growing under just the Juwel High lite system with twin T5s and they do fine. I'd try it with just those bulbs and reflectors and then only if that proves inadequate try and add more bulbs.

    Oh and make sure you get some good reflectors. I have some D-D gull wing relfectors which are really superb as their shape prevents light restriking the bulb.
     
  3. mjenner

    mjenner Member

    Messages:
    111
    Location:
    Chessington, Surrey
    Hi Ed,

    That's exactly what I was hoping to hear! I knew that the WPG rating method is misleading, and I definitely think it could be adjusted to account for the increased efficiency of T5HO bulbs based upon what you're saying. I remember reading in a few places that Glosso is typically recommended to be kept under high to very high light, which equates to 2 to 2.5wpg or greater, I just knew that my new lights were brighter than my old 4x18w T8's! :).

    It would be good to know just how much more efficient T5HO bulbs actually are rather than the marketing hype surrounding them, but I don't have the time or the equipment to work that one out! :)

    I've got the Arcadia T8 reflectors on there for now which seem to be doing a good job, but thanks for the tip about the D-D reflectors, I'll look into them next month when I get paid.

    Now on to the plant shopping list! :D

    Thanks,

    Matt
     
  4. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,953
    Location:
    Chicago, USA
    Hi,
    One ought not to compare the light energy of a T5 versus a T8. A T5 of equal wattage of a T8 is brighter almost by a factor of 2. It's not surprising therefore that the T5 bulbs appear brighter, because...they are brighter.

    WPG is a rule of thumb. It is not scientific and it's actually quite meaningless because the energy of bulbs varies quite radically. Also, the light energy dissipates quite quickly as the distance from the bulb increases. This is called The Inverse Square rule so for example, if you double the distance away from the bulb (say from 1 inch away to 2 inches away) the energy is 1/4th as much. If you triple the distance (say from 1 inch away to 3 inches away) the energy is only 1/9th as much. So a plant that is 8 inches tall and has the top leaves 4 below the bulb has a huge variance (9X) in energy input from top to bottom with the same bulb.

    Another myth is that HC, Glosso or Hairgrass require high light, or that you should add more light if they do not perform well. Carpet plants are high CO2. Clearly the inverse square rule is in effect because they are at the bottom of the tank but the real problem with their location is that the CO2 is very much lower at the bottom of the tank. That's really a more important reason these plants suffer. There is almost an inverse square rule with CO2 as it tends to escape from the tank. CO2 concentration levels are not equal across the tank. many people attempt to fix their carpet problems by adding more light when in fact they should be adding more CO2. Adding more light just makes their problems worse as this creates a higher CO2 demand. Adding reflectors intensifies the light even more so this is something else to consider. Do not follow WPG blindly.

    Cheers,
     
  5. mjenner

    mjenner Member

    Messages:
    111
    Location:
    Chessington, Surrey
    Hi Ceg,

    Thanks for that, but I'd thought that I'd hopefully addressed the CO2, nutrient and flow issues satisfactorily already (I guess I find out when I finally get the plants in), so the light was the only factor I wasn't quite happy with in my new setup. However now I've had assurance that the light level is indeed sufficient for (what I believe are) the most demanding plants I'm hoping to keep, I can concentrate on worrying about CO2, nutrients and flow if I find a problem with their growth.

    It's a shame there's no standard way of measuring light intensity given off from a bulb (without lighting meters), and then calculating the required intensity for a given depth of tank, it would be great to walk into a shop having done a simple calc given the dimensions of the tank, and buy lights that would give out n number of units of light, it really is confusing sometimes :).

    Cheers,

    Matt
     
  6. Superman

    Superman Member

    Messages:
    1,804
    Location:
    Cheltenham
    I tired to tackle the HC by giving it loads of light using a luminaire and then found that I was just causing and feeding the algae as my nutrients, co2 and flow were the issue.

    Having more light is better as you can grow more plants and quicker but it'll also mean that you'll have to have increased ferts, co2 and flow.

    You can always increase the photoperiod for light purposes rather than giving mass of light in a short space of time.
     
  7. mjenner

    mjenner Member

    Messages:
    111
    Location:
    Chessington, Surrey
    Hmm, definately good to remember, I didn't think about that, but I would imagine this would only be within certain limits though (eg adding an extra hour or two to the lighting schedule).

    You couldn't say for example leave an 18w T8 on for twice as long and expect it to be as good as 2x18w T8's for example.
     
  8. GreenNeedle

    GreenNeedle Member

    Messages:
    2,706
    Location:
    Lincoln UK
    Clive is on the same wavelength as me (although I get battered posting this idea on other forums. lol)

    T5 is much more intense. The PAR readings (which i cannot measure nor can most) will be much much higher.

    It's very hard to convince people when the long standing belief is carpets need high light even when you show them threads like the one where Tom Barr measured the PAR of the ADA tanks at AFA and came back with results that suggest they are much much lower than expected. People will always come back at you with Lumens and watts and technical specs of the units as it is 2 or 3 people versus a long standing rule.

    Maybe one day it will go the way of the excess nutrients rule but I doubt it will be any time soon :)

    In summary go with the lights you have. Good light (Decent tubes/intensity/Spread) is what you want and not necessarily just 'high' light technical specs. Then all you need is to guarantee good circulation to get the CO2 delivered to the depths.

    AC
     
  9. mjenner

    mjenner Member

    Messages:
    111
    Location:
    Chessington, Surrey
    Well, that's good to hear, it doesn't help when most local fish shops are giving terrible advice to people regarding planted tanks.

    I've removed the extra T8 and concentrated on getting the reflectors set right, should've gone with my Gut instinct rather than the WPG ratings.

    Regarding the WPG myth though, I think it'll continue to rear it's ugly head as a "standard" to work by until there's another more efficient standard, maybe some kind of "gas-mark" equivalent system using the PAR of the lights and their spread to rate on a scale so you could directly compare T8's with T5's for example.

    Then your requirements could hopefully be determined with a some calcs according to your tanks dimensions and the spread of the light required, and reflectors could be rated on the increase they give to the bulb's PAR and/or spread for the various types of bulb that the reflector fits?

    Ah well, it'll take a far smarter person than me to work that one out (and someone with a PAR meter, a lot of time and a lot of money to test all the equipment! :) ).

    Yes, I do agree with you, it's just one (or a few people vs a lot of people who "know" the WPG rule, but sometimes these new ideas propogate if you make them simple enough to use, publicise them and show that they're effective (look at EI fertilisation for example). Although I admit that actually doing those things in practice is a lot harder.

    Cheers for all your help,

    Matt
     
  10. JamesC

    JamesC Member

    Messages:
    1,276
    Location:
    Bexley, Kent
    I think we have to be carefull when comparing linear T5's and T8's. As Clive said above they may be twice as bright, but in no way do they give off twice the amount of light. A while ago I compared T5's and T8's in a thread but can't seem to find it at the mo, only a thread where I have mentioned the results. What I did was to go to various light manufacturers websites and compare the light output of their T5 and T8 tubes. The tubes I compared were of the same type except of course one was T5 and one was T8. The measurements they use are Lumens but this doesn't matter as the spectral graphs are the same.

    What was interesting was the difference that tube size made. These are an average of the figures I obtained:
    At around 18 Watt T5's ouput is about 35% higher than T8's
    At around 54 Watt T5's output is about 15% higher than T8's

    T5's are definetly better than T8's but not by the amount that most people seem to think. T5's also have the advantage of having a smaller diameter which reduces the amount of restrike when a reflector is used.

    Where people get confused is that they look at a T5 tube and a T8 tube and the T5 tube looks a lot brighter. The reason the T5 looks brighter is because more light is being emitted per area of tube.

    As an estimate of this we can determine the difference the cicumference of the tubes to work out the area difference. The results won't be 100% accurate as the two tubes have slightly different lengths for there equivalent Wattages but it's fairly close.

    T5's have a circumference of 5cm and T8's have a circumference of 8cm so T8's have an area of 1.6 times. Add to this the extra output of the T5's and this is what you should get:
    For 18W T5's ((1.6 / 100) x 35) + 1.6 = 2.16 times brighter than the equivalent T8
    For 54W T5's ((1.6 / 100) x 15) + 1.6 = 1.84 times brighter than the equivalent T8

    So yes T5's may be twice as bright to look at than a T8, but in total light output they are only a bit better.

    Maybe my theory is totally wrong but that's how I see it.

    I still like the WPG rule as it's still very simple to use, but it needs to be worked out differently for different tank sizes.
    For T5's: from 4WPG for nanos to 2WPG in the middle for 180 litre tanks and 1.5WPG for 300 plus litre tanks.
    For T8's add about and extra 1 WPG in smaller tanks and 0.5 WPG in larger tanks.

    Or another way is two full tank length T5's or 3 full tank length T8's is a nice easy to maintain CO2 setup.

    No doubt others will disagree with me as lighting is such a tricky subject to cover. Normally people think they need way more than is actually required.

    James
     
  11. GreenNeedle

    GreenNeedle Member

    Messages:
    2,706
    Location:
    Lincoln UK
    James - I agree on the WPG rule. It is there because it is easy to understand and there is no other way for the average hobbyist to get a gauge on what they need. Going into PAR means buying equipment and is not possible to convert into a guide for someone without a PAR meter because there are so many variables such as distance between the tube and water surface/substrate, length of tube, quality of tube, quality of reflector and many other things so this is why the WPG rule 'clings' onto existence. It is simply something that everyone can easily understand.

    However when you produce light from a smaller area you get a much higher PAR. Small point sources produce much more intensity which is where T5HO comes up as the top in fluorescent PAR wise.

    It isn't the most 'efficient' lumens per watt wise or on power consumption. That title goes to standard T5 linears. 2 tubes of T5 linear of the same wattage as 1 tube of T5HO has much more Lumens but importantly because of there being more light produced from a smaller area on the T5HO then the PAR is higher!!!.

    This has been shown for LEDs where the marine lot were bashing the LEDs versus MH for not being as powerful per watt. They were wrong and far from their corals dying they were bleaching from the increased PAR. The LEDs used had much less Lumens per watt than MH but in contrast the LEDS had much more PAR per watt than the MH!!! No I have no readings for this either :)

    This is the trouble when using Lumens!!! I am seeing this with my LEDs. I have been told the total is actually 37W which = 1.1WPG compared to the 48W of the fluorescents which was 1.45WPG. The total light due to the sunrise/sunset staggering is much less overall than I used on flourescents but the growth is much more. I have been raising the luminaire up to try and get the growth to equal what it was previously and they are currently 15" above the water line whereas the fluorescents were 4".

    I would guess there is a similar (not as much of a difference) effect from using 5/8 inch tubes and 1 inch tubes.

    Many people have tried better rules of thumb but as it needs to be something the hobbyist can use then they always go down the Lumens route which we all know is about as good as using the WPG rule. lol

    There won't be a solution unless PAR meters come down to a tenner. :lol: which we know will never happen.

    I have said for a while T8s on electronic ballasts are pretty good. much better than the WPG rule suggests for T12s. there aren't so many good reflectors around for T8 though. I tend to suggest T8 is 1.25x the WPG rule and T5 is 2 x, however this is based purely on plant growth observations and the quality of reflectors available and affordable for each.

    I would go as far as to suggest 3 x T8 18W (54W) is much much better than a 55W CF due to several things. the reflectors available for T8 are much better than CF. They are individual reflectors whereas the CF has 1 reflector behind was is in effect 2 T5 tubes and most importantly you can space the T8s whereas the CF you have no option to do this. Therefore you get a much better spread of light in the tank with the T8s. This suggestion got me in big trouble on the American dominated sites. They are obsessed and very defensive of their 6WPG of PC/CF/PL setups :)

    AC
     
  12. JamesC

    JamesC Member

    Messages:
    1,276
    Location:
    Bexley, Kent
    This I don't agree with. Isn't PAR just a measure of the amount of light, the same as lumens is, but over a different spectral range? If you have a light that emits light over 2 squared cm and then you cut the area in half to 1 squared cm but also double the power so twice the amount of light is emitted, then the total amount of light emitted is the same but the intensity would be doubled. Or have I got this totally wrong?

    James
     
  13. GreenNeedle

    GreenNeedle Member

    Messages:
    2,706
    Location:
    Lincoln UK
    I'm not absolutely sure of this part. Something to do with penetration I think but no techy expert.

    PAR is a measure of radiation whereas Lumens are a measure of light output.

    PAR measures active radiation at the point of 'receipt'. PUR will measure usable radiation at the point of receipt. Lumens measures the output at source.

    Therefore 1 tube's Lumens will match another of the same brand/age etc within reason but the PAR will depend on where it is situated in relation to the 'target'.

    I have just read a lot on the benefits of smaller point sources in relation to PAR but I can see where you are coming from. I will have to research it a little more to find the 'reasoning' :)

    AC
     
  14. JamesC

    JamesC Member

    Messages:
    1,276
    Location:
    Bexley, Kent
    Mmmm, you have a point there. A bright point source will definetly penetrate further than a larger light source even though the light output might be the same.

    Be interesting to see what you find out.

    James
     
  15. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,953
    Location:
    Chicago, USA
    James,
    Lumens and PAR have nothing to do with each other. It is a measure of the "perceived" intensity based on the frequency response of the human eye. So the measurements are always normalized using the "candela" definition which has nothing to do with actual delivered energy content. PAR measures the actual number of photons (moles of photons) crossing a unit area, per unit time. This is a significant difference because of the way photons interact with chlorophyll. One photon colliding with a chlorophyll molecule ejects one electron. The photon energy absorbed in the collision is closely related to the electron energy gain, so it absolutely matters how many photon collisions are occurring per second over a certain area. PAR measures the number of potential collisions which can directly be converted to an equivalent amperage (electron movement). The most a Lumen measurement can say is how bright something "looks" compared to some arbitrary brightness based on 555 nm wavelength light standard. Since photons are delivered at every frequency in a bulbs spectrum these two measurements are not even comparable.

    So I'm not sure what to make of the surface area comparison or of point source versus large area because PAR is normalized by area so it doesn't matter how wide or thin the two bulbs are, PAR would measure the same unit area on each bulb and would simply count the number of photons being emitted per second across that unit area.

    So when you looked at the lumen comparison of the T5 vs T8 all that can tell you is how much more your optic nerve responds in resonance to the 555 nm light from a T5 vs a T8, but what we need to know, really, is the cumulative number of photons from every wavelength that each bulb produces, and which actually crosses 1 square centimeter of that bulbs surface in 1 second. This is the only driver of "penetration". If 1 square centimeter of a T5 bulb emits 20 million photons per second but the T8 only produces 10 million photons per second across the same area of it's surface, then it stands to reason that 1 foot away from each bulb, twice as many photons (or some ratio due to inverse square rule) will arrive at that 1 foot destination from the T5 bulb. The only effect of thick versus thin would be possibly the emission pattern from each of the two cylinder shapes. Ultimately though the PAR meter can measure this easily.

    When it comes to plants we need to stop thinking of brightness in terms of lumens which is meaningless and instead in terms of payload delivery rate which is converted by the plant back to a form of electrochemical energy. This make WPG much more palatable.

    Cheers,
     

Share This Page

Facebook Page
Twitter Page
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice