oldpunk78

i just started my first low light tank and i'm not quite sure if i got the lighting aspect right.

tank: 36L x 15W x 20T (about 46 gallons)
light: 2 x 21W T5NO (home made, can also raise and lower as needed)
substrate: mineralized top soil capped with fine gravel.
plants: anubius, crypts, ferns, bolbitis, ect.

i'm gonna have to assume that my fixture puts out about as much light(maybe more) as a 36" coralife T5NO fixture.

what should my lighting period be, and how high above the tank should i start out?

thanks in advance.

- josh

dyollnave

Two 21 watt tubes in a 46 watt tank is almost 1 watt per gallon. I have heard of people going to 1/2 a watt per gallon on a 37 tall with acceptable growth on their anubius. Personally i love lots of growth so i would put the light as close to the water level as possible. the power of the light drop off with the square of the distance so the further away the lights are, the weaker they will be. A photo period of at least 8 hours is needed for growth especially in a low light tank such as yours. you can get away with shorter days if you have more light. (My lights are about 3 inches from the surface, 8 hour period, and about 4.5wpg and I have more growth then i know what to do with)

oldpunk78

i thought the WPG rule didn't apply to T5...

my 29 with 48w T5HO totally needs co2. this tank is lit up just about as good. i don't get it. to me, i'd have to say that i have the equivalent of about 1.75 WPG+.

armedbiggiet

WPG rule is not good cause it did not consisder distance also T5's wave length travel better than most of the lights.

armedbiggiet

Looks like it should be just enough not to kill them but to grow them you might need one more 21w... they are low light plants but that does not mean they don't need high lights and bolbitis is a good example as it would do much better in brighter tank.

oldpunk78

i don't know dude... after i made this fixture, i wanted to 'gauge' how bright it was. i have a 96W PC fixture with a bulb that is about six months old in it. after seeing them both on the same tank, i was surprised to note that my home made T5NO fixture was slightly brighter and had better coverage than the PC fixture. (i wish i had a PAR meter)

so with that being said, i don't think i need anymore light. but i'm still wondering about the photo period. i've noticed some folks are doing a rather long photo period(14hrs.?) with a "siesta". what's that all about?

dwalstad

Here's a link to the photoperiod discussion you're refering to:

http://www.aquaticplantcentral.com/f...ic-plants.html

There's also a later thread entitled "Daylength Revisited" where I've included the scientific references backing up my recommendation for the 12 hr minimum daylength.

If you want, I would give your plants at least 12 hrs of light. The Siesta regimen is just a nice refinement; it allows you to give your plants the 12-14 hr daylength without keeping the lights on for the full 12-14hr.

oldpunk78

thank you ^

that's what i was looking for.