How much light is enough for live plants

I bought a 20 watt Flora fluorescent bulb for my 33gallon tank (16-17 inches deep). It said 90LUX on the box and that it is ideal for planted aquariums. I only have space for 1 bulb. Is that enough light for live plants?

 

Short, official answer: No.

My answer: No, but...
I have a 30 gallon tank with just one normal bulb in it. My plants are flourishing. The Java Fern has split several times. My myrmio (a high-light plant) grows fast enough to keep Miyamoto and He Who Eats Snails happy with snacks. The chain sword would have done wonderful if the above-mentioned fish hadn't ripped it up, plant by plant. My micro-sword is slowly spreading, etc...
The one thing about my tanks that might be different is that the room they are in is pretty bright. They get no direct light, but the room does get quite a bit of filtered sunlight that reflects off of all the of white/light-colored surfaces in the room.

 

yeah, that's what I was hoping. The family room where the fish tank is has skylights so the aquarium does not get direct sunlight but the room is bright. I guess I'll just have to try... Any recommendations for low light plants? I'll have to get some of the java fern.

 

It sounds like you've got the same setup that I have, so I'll just tell you what I've got that's working out. You can also go toplant geek. I just love this site. It allows you to browse aquarium plants based on light needs, brackish adaptability, placement in the aquarium, etc...

I've got Java Fern that's working well. Water Wisteria seems to be working out, too. I would strongly suggest using gloves or tongs when handling wisteria. It seems that it has some type of spines, or else I'm just allergic to it. In either case, I have a reaction similar to a very mild case of stinging nettle when I handle it. Chain sword. Micro-Sword. Myrmio (I've got red myrmio, but green probably would work, too). Anubias (I think I've got dwarf anubias), and anacharis (unsure of spelling) This last is a very hardy plant that can grow while free-floating, allowing it to soak up a lot of light from even weak bulbs like our fluorescent bulbs.

 

I bought a 20 watt Flora fluorescent bulb for my 33gallon tank (16-17 inches deep). It said 90LUX on the box and that it is ideal for planted aquariums. I only have space for 1 bulb. Is that enough light for live plants?

It depends on what plants you have. There are low, medium, and high light plants. Your tank is 33 gallons and your lightbulb is 20 watts, which gives you 0.6 watts per gallon of lighting (33 gallons / 20 watts = 0.6 wpg). Maybe some very sturdy low-light plants would make it in your tank, but don't be surprised if they died. Although, you can always try, right?

I personally think even low light plants should have at least 1 wpg of lighting; 1 - 1.5 wpg is probably best for low-light plants. Best low light plants are Anubias, Java Ferns, and Java Moss. In my experience, Water Sprite and Hornwort do quite well under low light too.

P.S. What is the spectrum range of your 20 watt lightbulb? It should say on the lightbulb's box (it's measured in Kelvins, for example: 6,700 K, 10,000 K, etc ...). The best lightbulbs for a planted tank are those up to 10,000K but not above 10,000K. Those above 10,000K have a lot of blue spectrum in them, and the blue spectrum encourages algal growth. I personally use the spectrum of 6,700 K and I love it. Very good for plant growth and a very natural color.