Grow Lamp supplement

[aquaarche]

I bought 2-20watt 24 inch fluorescent grow lamps with reflectors. the lamps emit 10000K of full spectrum light. I bought them to supplement the sunlight for my aquaponic's in a barrel system. I have tomatoes seedlings, marjoram, Basil, celery and Lettuce. At what distance should the lamps be from the plants to be effective? Currently they are set at about 30 inches above the grow bed and the plants are reacting to the lamps since I placed them above the beds.

By the way guys I made my fist harvest from my 45 gallon tank of 8 pieces of the most clean tasting Tilapia I have ever had.

I have harvested lots of lettuce. My tomatoes were just a small type but this time I planted big ones to see how they will do.
any advice on how to keep the tomato plant short say 2-3 feet. My last one grew to 8 feet tall and produced 25 small tomatoes.

I am having success keeping the water at 6.8pH Lack of Sunlight seemed to be some of the problem as to slow growth or little growth. I hope the grow lamps will help supplement the needed sunlight.

[urbanfarmer]

I would keep them as close to the plant as possible with the most exposure to the leafs. In my experience 2-3 feet is too far. I would make it only a few inches. Of course this will mean you need to check it regularly and adjust the lights. If you don't have it setup for that, then keep it wherever is most convenient for you, but as close as possible.

The "power" of the lights are rated at 1 foot from the light. At 2 feet away your light is 4x times WEAKER. At 3 feet away your light is 9x times WEAKER. At 4 feet away it is 16x WEAKER. I think you get the picture. BUT, if you place the light at 6 inches your light is TWICE AS STRONG (relative to the plant)!!! Mathematically, the closer your put the light the closer the light reaches an infinite energy (however, this is not quite correct in reality).

I am currently taking advantage of this phenomenon with my seedlings. I have some in cups, and I place a single cheap store bought CFL light above them. I have experimented for fun, and the seedlings I place the light almost touching the plant grows like mad whereas the ones about a foot away grow slowly and sometimes bend toward the window even though the window blinds are down... which tells me the light is really weak if the plant would prefer weak filtered sunlight.

[grimsteph]

In order for fluorescent lighting to work well, it has to be placed extremely close to the plants.

[badflash]

Plants don't care what direction the light comes from. If the plant is tall, light it from both sides.

[urbanfarmer]

Plants don't care what direction the light comes from. If the plant is tall, light it from both sides.

According to the information in the book below, that is not true. The full text that is relevant is available online.

A Companion to Plant Physiology, Fourth Edition by Lincoln Taiz and Eduardo Zeige
http://4e.plantphys.net/article.php?ch=t&id=131

I have also seen some cutting edge research (granted it was a few years ago now) that showed that plants have sleep cycles. If you leave the plant in the light 24 hours it will change the direction of the leafs so the light hits it perpendicular or covers itself up, which shows evidence that the light direction also matters (but this was not the point of the research, just saying...). If you look at the research above you will see it's more complicated than that, but it is interesting.

[badflash]

Photons are photons. Just energy for the plants. The leaves turn to the light. Pot growers have known this for a long time. Plants need a rest time to deal with starch production. Lots of light they store starch. No light they build cellulose and grow. If you want legal plants, us a reasonable day/night deal. I like 16 on/8 off.

You also have to deal with fish. For tilapia 14 on/10 off seems to be good.

To get the right intensity with bulbs is impossible lighting from the top. Sides works better. Light is closer to the active leaves.

[aquaarche]

In case any of you are wondering why the lamps are 10000k each they were the only plant growth lamps I could find in Palawan. Normally these are used for fish tanks. so the reason is they put 6500k lamps 12 inches from the top of the plants and so I was wondering about how far to put 10000k. normally at 3000-7000k the lamps are 6- 8 inches above the plants. but I can find no info on 10000k lamps placement because many don't use that high a kelvin rate. I will lower them down half of the current distance I have them at now and raise them as the plants grow.

[keith_r]

i just re-did my lighting on my basement system this past weekend, i had a 450w hps growlight and 1 shoplight w/ 2 t12 daylight flourescents.. i pulled out the hps and put in 2 t8 shop lights (they were $9 and change at walmart, went up .20 sunday, i opened one light and the frame was mashed in so i returned for a replacement)
pulled out the brocholi and basil, planted a few things.. i found some french radishes, i swear they started germinating sunday night and already up to 1/2" tall, green onions just started sprouting, i also planted carrots, eggplant and fennel
the lights are hanging about 12" to 16" above the growbeds and i kinda wrapped it all with foil, lights are on a timer for 14hours a day

the t8 lights are 32 watt, i think the t12's are 40 watt

[urbanfarmer]

Why did you swap out the 450 Watt HPS?

[keith_r]

to save money!