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Bit lost in the Luminaire Jungle, new Project


Expert/Global Moderator
11 Jul 2007
Chicago, USA
Well, there is always an "argument" which consists of determining the relative merits of one idea versus another. The term argument should not be automatically construed as being associated with hostility. We are using logic, rationale and science to determine the proper course of action, therefore we must depend on logical, rational and scientific arguments.

In general, very roughly, T5 are claimed to output around 50% higher energy levels over the equivalent wattage T8 bulb. If reflectors are being used the output will be magnified. Again, very roughly a 20 watt T5 bulb may appear to be as bright as a 30 watt T8 bulb (of the same phosphor rating of course). So yes, you'll be adding more juice by way of T5. Don't hold me to these numbers - I'm just using them as instructional :!: Based on the explanations given previously this virtually doubles the amount of photon bombardment. So the implication is that for a higher energy light source your nutrient, flow and CO2 requirements will be more stringent. If you did have a PAR meter, as SuperColey mentioned, you would be able to do a precise photon flux density count and to compare the actual output of the two bulb types. I believe the point he was trying to make was that in the absence of a PAR meter, or other quantum measurement device, we can only roughly judge the amount of photonic energy being seen by each leaf. Someday, when PAR meters become commonplace, we will no longer need to talk about watts. We will talk in terms of the number of photon energy packets moving across one square centimetre of leaf surface per second. This is described in terms of a Mole. One mole of particles is 6.023 x10E23. One micromole is 1 million times smaller so a "umole" 6.023x10E18. PAR values are expressed in terms of umoles. Therefore we can accurately describe the lighting in a tank as "I have 100 umoles at the surface declining to 30 umoles at the substrate level". This more or less describes a low light tank. What wattage of what bulb and what lumen value the bulb is rated to, and what Kelvin value it has can then be ignored completely because we have a direct count of the number of electrochemical reactions caused by our lighting. And this is what photosynthesis is about, not about lumens or Kelvin or any of these other time wasting parameters that have stifled our thinking for the past 30 years. SuperColey's "argument" is that you need to change the way you perceive light so that you think in terms of umoles/cm/second of photons and not lumens, which are totally and utterly irrelevant.

I also think that you cannot engineer your scape as you propose without a great deal of work. As SuperColey suggests, just get a nice even lighting across the tank at the energy level that pleases you and get on with it. Of course plants grow towards the light, that is their nature. What Barr was saying is that many people assume that when their plants grow stringy this means that it needs more light. Carpet plants are notorious for this behavior. People add more light to try and get them to grow laterally and this just creates more problems. Barr is saying that adding more CO2 satisfies the plants needs at the submersed level so they do not seek to grow upwards to get to the surface where CO2 is. I'm fairly certain you've confused these two concepts.



19 Jul 2007
Lincoln UK
Indeed. I should clarify however that I do not have nor have access to a PAR meter. My input is from observation only with no way to prove anything. Others are doing the actual testing and there are several people all comparing lights they have with what they can borrow and then trialling different spacings and different heights to see how it affects the overall PAR.

then those multiple sources can be gathered together and once the difference in ballast / reflector is taken into account we should be able to weight the 'average' towards the most common place used items rather than just a mean average of the figures of people who are testing 'top end' stuff. that would give false info. We need rough guidelines for standard performance items.

No good giving an average based on 3 x Ice cap units and 1 x cheapo. People buying a cheapo would then be thinking the 'mean' average is going to be attained when they are way off :)

As a guide, when Tom tested some ADA competition placed tanks with lush carpets of HC in them the PAR at the substrate levels was 50ish. As per what Ceg said above, that is surprisingly low light for a plant the majority tell you needs super highlight to carpet ;)

The next big bang in the hobby is just around the corner and it could be more destructive to the commonly 'known' thinking as the Phosphates DO NOT cause algae breakthrough.