Need help with Light intensity for my seedlings

The seedlings look like they are stretching. You need a light meter (!) I personally use a Dr.Lux meter and start my plants at 20,000 lux (at the canopy).
There are some apps you can use on your phone that emulate a light meter, some members say are pretty good.

 

seedlings at this stage need more heat than light, 72-79F is good best 77f
I do use a heat plate and a low end floro, works well

you not mentioned the soils but cutting with 30% perlite at this stage and this current result will work well

check the link: Nutrient Burn

good luck

 

Im in europe and for years have suffered bad mold, to counter that I use stretchy lights/ 2400 kelvin or hps thru out my grow,
having slightly stretched plants allows the air to circulate amongst the crowded leaves and flowers,

tho later a couple of weeks of cool white is good to encourage normal growth,

forget the perlite then if you are happy with what you got

not to be confused where plants have not enough light and stretch full time to get that required light, note the light color of 2400 kelvin stimulate the auxins/hormones, making the plant seem slightly stretched, cool white light 6500 kelvin does the opposite and makes squat plants

good luck

 

An old trick is to lightly flick the plants or have an oscillating fan that can swing some air currents on them. This will help a lil to reinforce the stem. Not sure what tropism is at work here (thigmotropism?). Also, you can bury the plant deeper when you decide to transplant. I put a bit of rooting compound on the stalk when I do this.

that is good.

which is why I see nice plant growth off 5000K. I bought a couple older Samsung lm561c strips for $3 (per 2' strip) and they work so nice for this.

I wouldn't recommend this; shorter internodal space can be controlled by pruning but long internodal space is not so easily treated. Anyhow, defoliation and training ftw.

that is good, but I should point out that idk how accurate those apps are. I use my light meter quite a bit more than I ever thought I would...

 

I don't understand the seedling stretching when it's getting hit with 180w @ 60cm/24 inches. For the first 7 days of life, my auto seedlings are under a Mars TS 1000, necked down to 75w @ 46cm/18 inches with absolutely no stretching. I'm baffled.

 

That's what's puzzling. I know when there is insufficient light, the seeding releases a hormone causing the cells in the stem to rapidly elongate in an effort to get closer to the light. But with your Mars set at the parameters you describe, light shouldn't be a problem. You might try this @Aricel - add medium to within 4cm of the cotyledons for support and as @trojangrower suggested, add air circulation to strengthen stem and root system.

 

@Vee makes a valid point that should be recognized.

color temp much more important than some realize.

...but you have a similar light so dropping down the extra 14cm might be the ticket. I would note the app's lux reading for future use.

and the app... again, its a secondary go to and shouldn't be considered as a valid point. Additionally, the amounts of photosynthetic active radiation (PAR) measured by lux instruments (except for quality quantum meter$) is only a general illuminance; it doesn't pick out the color intensity and only gives a ballpark value; so using a lux or phone app is not the best for determining accurate values. But if you get to know your device, and record it for future use, it will be useful.

yes! add some soil, bury them stretchers

 

tropism
trō′pĭz″əm
noun

1. The turning or bending movement of an organism or a part of an organism in a particular direction in response to an external stimulus such as light or gravity.

I prefer the word photo - morphism, bending to the light, tho tropism means any thing that moves the plant
I thought I was the only one who buried deep ..lol, agree about the light apps, I still drive Lux and convert to PAR when I have too, by x1.5=

we swim the same direction

cheers