How To Calculate Light Needed For The Plants?

[drabina]

I have a 10 gallon tank with the following plants: java fern, anubias nana, moss ball and some ludwigia repens and dark red. If my LED light produces 10W of power, how many hours should I keep it on for the plants to grow and stay healthy? I have a low-tech tank and I only feed fertilizer once a week (NilcoG Thrive). The moss ball and anubias nana are in the tank for a couple of years now. Java fern and ludwigia are new to the tank. My current light schedule is 1.5 hours in the morning and then 6.5 hours in the afternoon till the late evening. This gives me a total of 8 hours plus the natural light during the day but aquarium is not by the window so only gets reflected light. In the winter months, that's not a lot of additional light.

 

[-Mak-]

Plant light is measured in PAR, here's a really good read on that:


8 hours is typical

 

[SeattleRoy]

HI drabina

We may not be able to "calculate" the amount of light at the substrate level of your tank so much as a rough "guessimate". Why, because the efficiencies of the power supplies, LEDs, and circuitry of all the manufacturers are different. The only way to get an accurate reading as to the amount of light is with a PAR meter.

I have a 10 gallon tank with two (2) 7 watt / 35 horizontal corn lamps (14 watts total) installed in an old incandescent fixture. The two lamps provide the plants / tank PAR@30 measured at the substrate level with an Apogee MQ-510 PAR meter which is considered "low light". "Low light" isn't bad, it can certainly support plants that tolerate low light such as cryptocorynes, mosses, Microsorum (java ferns), and Anubias just to name a few.

Here is my 10 gallon, low tech but with ferts and liquid carbon, PAR@30 tank



And here are the lamps I used (E27, cool white, 7 watt)

 

[angelcraze]

My 5.5 gallon with a 10W diode chip LED light is low light at best at the substrate. 30 PAR and under is considered low light. But obviously you can grow a nice looking tank with 30 PAR at the substrate (distance from light source to substrate). Just make sure there is sufficient coverage over the length of the tank unless you are ok with a island-style tank where most of the plants are directly below the light source. The corners would be shady. You might require two 10W bulbs to grow the whole footprint of the tank.

I use two $$ store 6W LED bulbs for my 15 gallon. It's even less light than the tank above, meaning the plants are lower light plants and simple, but it grows my plants nicely.


It's my blackwater tank, but the java fern exploded. Crypts look nice and compact too.

 

[drabina]

Thanks guys. I have no access to a PAR meter so I guess I will just keep the light for the 8 hours a day and see how the plants are doing. I know that ludwigia will loose bottom leaves if there is not enough light. If that happens, I will have to increase number of hours.