That's interesting about the Java Fern. I've got some browning leaves with lots of daughter plants. And at the roots, lots of green new growth. When I bought the plants they had a few brown specks...hardly noticeable...now there is much more in 4 weeks...maybe flaws in lighting and water conditions?
I measured the distance from my present bulb (T8 8000K Daylight NO 15W 18 inches in a reflector at tank top about 1 inch from water level) to the substrate and it varies from 12 to 15 inches.
Went all over on Sunday afternoon looking for daylight T8 bulbs 15W at 6500K or 6700K...all sold out at the hardware stores except one that was broken
Also looked at CFL bulbs but the boxes listed lumens instead of Ks...so I am confused here. It seems that the dimmer bulbs had high lumens than brighter bulbs? Really confused as to what a lumen is...
Question: can I put 2 T8 6500K 15W bulbs on my 20 gallon (and get more even lighting obviously) but at 12-15 inches from the substrate is this going to be enough light for Java Ferns and Anubias and hopefully some Dwarf Saggitarias? I think I am still in the low light PAR range? (If PAR is intensity of light reaching through out the tank width and is also influenced by the depth?) And 6500K versus 8000K is describing the color intensity of the bulbs...so the color spectrum at 6500 is better for plants?
Maybe I just hang a couple of CFL lights in reflectors from the ceiling?
I found it odd that in the hardware stores there were so called aquarium bulbs marketed as good for plants that were T8 15W and only 3000K? I stayed away from those...
Just trying to understand...so much to learn!