what shoudl my light watt be

I've bought a fair amount of plants from a local breeder. He has a heavily planted 75g with several species of plants. I've asked him about his lighting and frequency. He has 2 40w bulbs from Home Depot and they light the tank for 6 hours a day.
 
I just didn't much like the statement that you need above 30 watts in a 20 gallon to grow most low light plants because I haven't had too many problems with my plants and i've only got a 15 watt is all <333
 
Growing plants and what "plant tank people" consider growing plants are two different things. To tack on 1/4" of growth over a couple days is all fine and good, but can hardly be considered really growing a plant. Adequate lighting makes for a lot of growth when coupled with CO2 and nutrient levels being balanced, and to try to quantify that to someone who has never had it is very difficult. If you are making your plants grow with a 15W fluorescent over your 20L, that's cool. What people here are trying to say (I think) is that in order to make for a lot of lush green foliage with low-medium light plants you really need another 15W at a bare minimum. Just my thoughts.
 
If you have a drill and skil-saw you could easily put together a CF fixture with all the pieces coming from Home Depot. I did mine in about three hours. You'll need:

2 Porcelain Lightbulb Sockets (Electrical)
14' of "zipper" cord (Electrical)
2 E-Z Wire Plugs (Electrical)
2 27W Philips Daylight CF Bulbs (Lighting)
1 Strip Socket (Lighting)
1 Small Sheet of Plywood (Bldg. Materials)
1 1x4x8 Pine (Bldg. Materials)

Build a plywood/pine box, wire it with the 2 sockets, screw in the bulbs, plug it in. Use the strip socket as the switch and you're on your way. All said it cost me about $80 to put 108W over my 55, so it should cost about $40 to put 54W over your 20. If you're willing to put in a few hours they end up working wuite nice. Also, since you're not retrofitting your fluorescent hood, if you have a glass top on the tank you can add 15 additional watts by continuing to use your fluorescent hood as well. Just my thoughts.
 
twig said:
I just didn't much like the statement that you need above 30 watts in a 20 gallon to grow most low light plants because I haven't had too many problems with my plants and i've only got a 15 watt is all <333


You probably wouldn't require all the fertilizers & C02 that you do if you just gave your plants enough light to begin with. Growing plants in a low-light situation doesn't usually require ferts. C02 is nice when balanced with lighting, but is definitely not required. Low light plants = low maintenance.

Beatle-- Most aquarium plants come from tropical regions that get about 10 hours of sunlight per day (+ dawn & dusk light). To grow plants well, 10-12 hours of light per day is usually recommended, particularly if the plants are not doing well (as is the case here).
 
Unfortunately I do need ferts. My corkscrew vals started melting before I started weekly doses of potassium. My Anubias and hygro started growing like crazy when adding co2 :O

my tank had 0 nitrate so I was getting a lot of BGA =/

I suppose it depends on the low light plants you get, though :O
 
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