PUR cannot be dismissed as some lighting experts have attempted to do based on their short time in the professional aquarium keeping industry, as we have already clearly established (as per the Overview section) that we found that once more precisely tuned spectrum fluorescent lights became available, we could grow aquarium plants more efficiently and with some advancements, this made the difference of not keeping photosynthetic marine organisms at all!! I should note that some of these advancements were comparing apples to apples; T12 to T12 such as a warm white to a Trichromatic or an actinic (which rules out lumens per watt and other measurements and leaves the FACT of PUR).
The beginning aquarist is likely to think that if there's enough light to see then it's enough for plants to grow.
However, that's not true. If you want to grow healthy plants, and not just algae, you need enough light for them to use for photosynthesis and create energy.
It used to be that people advised 3-4 watts per gallon as a VERY basic principle. But, due to modern lighting technology this is now considered an outdated notion (with PAR now more the norm).
This is a process that is powered by the energy of light
It is also noteworthy that many "terrestrial plant lights" as well as many aquarium plant lights (often of lower in kelvin temperature) have more "red nanometer spikes" than higher kelvin 6500k, 10,000k & higher lamps.
The problem with these lights is that while all plants utilizing photosynthesis require the same essential ABCs of PAR (see the PAR section), the facts of light energy penetrating water requires higher kelvin (6500k +) be added to provide maximum PUR (see Useful light energy/PUR section). Aquatic Plants and corals have adapted/evolved to the natural light energy at certain depth of water and the misguided attempt to adapt these terrestrial plant lights is not going to be 100% effective as a light with more water penetrating blue & slightly lower red nm energy.
23/03/2015 · Aquatic Plants: Rate Of Photosynthesis
Lights as they apply to aquarium use have evolved/changed considerable since I have been in the hobby & professionally employed in aquarium set-up & design.
We often used "hardware store" warm white T12 fluorescent lights, just in larger "quantities" to make up for the poor "quality" of light, even while planted freshwater could be kept, not so with ANY photosynthetic reef life.
Early on lights such as the "Aquarilux" came out which still was heavier on the "warm" colors, it also had more blue.
Later the Trichromatics & Triton lamps came out with spectrums focusing on the daylight 6500 Kelvin temperature, these made growing planted aquariums easier with less lights to do the same job as earlier lights.
We also had actinic blue lights become available, these mixed with other lights made it possible in the beginning to keep some photosynthetic reef life, although initially these did not thrive. Later T6 & T5 advancements along with Metal Halide lights allowed us to not only keep delicate photosynthetic reef life, but for this life to thrive.
We now have T2, SHO, & LEDs of which the later have lowered considerably the input energy for the quantity of output energy of light that we need for our aquarium keeping applications.
world with use as an aquarium ..
*GH (general hardness): 100 ppm or sometimes higher; this is more important than many realize for planted aquariums.
During photosynthesis, a rise in pH can occur in water with low alkalinity (20 to 50 mg/L) or in water with moderate to high bicarbonate alkalinity (75 to 200 mg/L) that has less than 25 mg/L hardness.
Aquatic Plant: Photosynthesis In An Aquatic Plant
This is an often misunderstood aspect of aquarium plant keeping.
There is so much anecdotal information that is out of date with more current aquarium/plant biochemistry information. Not only do plants need many of the minerals found in GH, but, just as important, potentially dangerous upward pH swings can occur if your GH is much below 50 ppm during peak plant photosynthesis.
For example, I observed a pH of 6.8 in the morning and then a pH of 7.4 in the afternoon in a tank where GH was low or almost non-existent.