Seedling light hieght

so this is my first post on here. ive started my first indoor grow and ive got some seedlings now that im running under a 400 watt mh. my question is about height. i dont have the best ventilation and i need to go get a new fan and the temps are between 70-85. the seedlings are 3 days old and ive got the light about 18 inches from the tops and they seem to be ok but im wondering if maybe i have it too low but i dont want them to stretch on me. any comments?




Everything ive said here is purely hypothetical.

so i raised my light to 28 inches and when i woke my best seedlings were starting to get a yellow tinge to them.

kodiak7 said:

so i raised my light to 28 inches and when i woke my best seedlings were starting to get a yellow tinge to them.

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What kind of medium are they in? Do you have pictures? It's so much easier to diagnose a problem with a picture. The height of your light depends on the temperature being emitted from your light source. Place your hand under the light at the highest plant top and if it feels like it's "too hot", it probably is. Treat the plant like you would want to be treated! I personally like to keep my light relatively high for the first few days then they come down in 6 inch intervals until I've reached what I consider the light being just right for the heat. Then I just follow the plants growth by slowing raising the light. Most people would say 12" off the tops for 400w, 18" for 600w, and 24" for 1000w (without any type of cooling).

unfortunately i cant take pics at the moment i need a new usb cord. anyways they were started in jiffy peat pellets and when i saw a root coming through the bottom i transplanted into solo cups with 2 parts FF happy frog and 1 part perlite. the thermometer i have next to the light stays between 80-85 and i have fans going. it doesnt seem to be too hot just good and warm on my hand. the leaves look like they are veined with a lime green/yellow color.