Light Questions: I didn't get it

[sfchung]

I have been reading up the threads on lighting requirements. However I am puzzled by the measurements used. I see watts/gallon used pretty often. I'd think that wattage of bulbs and and so on reflect the consumption of electricity by that particular appliance. And certain bulbs are of different efficiencies If we are trying to stimulate plant growth, shouldn't the measurement be on the intensity of light received by the plant (ie lumens or some other measure? ). So would the measurement be lumens/gallon or some other base? Would you think lumens over a sq ft base rather than volume makes sense? I took depth out because I thought it wouldn't factor much as std tank depth doesn't vary much in this hobby 18 to 24in. And you wouldn't have a 10 in tank depth would you?? Due to diminishing light intensity as you go deeper, you would probably ended up with different plant types as depth changes. But over a 24in depth, not many options are available.

To make the discussion more complex, probably need to introduce lightwavelengths in as well as plants respond to different wavelengths?

[dc88]

Its all approximation and general guidance. The wpg people talk about here generally refer to flourescent tube. Sure you can drill to the deep on quantitative light wave and enegry if you have the tool and money to spare. But if you just want a similiar result as the other guy's 72w 6500K PL light over his 2 ft tank, then just copy and why bother the rest of the details.

[AquaObsession]

I wish to say that, when it comes to planted tank, each is unique in some ways, and the watts/galloon is a rough estimate. There are many many factors that affect plant growth, which are nutrients, Co2, lights, temperature, substrate, parameters of water, and so on and so forth. Hence why spend a lot of money to measure the lumens or par value (not sure if i am even saying the concept right). And you will still need constant observation and maintenance for the plants to grow. In brief, there is no magic rule. [This reflects my opinion]

Once I had a 2 feet planted, and I've use lights as much as 36w, 55w, or even 110 watts, or a 150w MH for it. You have to adjust your nutrients dosage and Co2 accordingly, or even your lighting hours.

I see this is your first post in AQ, so welcome, and welcome to ask these questions. A search function will also allow you to obtain many answers on that.

Maybe expert aquarists are playing with all these lighting factors, but most of us (amateur) are simply experimenting with growth under various conditions, and adopting the methods which give us fair results given the effort and $$ we put in.

[sfchung]

Thanks for the feedback guys. My questions were triggered after looking at the costs to light up the tank, especially the T5HO ones. Am trying to make sense out of it as it wasn't always clear whether visbility was the objective or plant growth.