Light versus heat during Veg

I recently upgraded my lights with an SF1000 along with my 300 watt blurple light. I have a 2x2x4 grow tent, which is too small anyway, but I can’t upgrade just yet. I have a single ILGM Sour Diesel growing in there in a 20 gal DWC container. She is in her 2nd -3rd week of veg. No matter what I do, I cannot keep the temp down below about 77F /24C. I have been cooling my nute solution crudely with reusable ice blocks to keep that temp down to 70-71.

It has been really hot here and I can’t afford to keep my house cooler than about 75. The basement where my tent is does not get much circulation and has been staying warmer.

So, my question is would I be losing much if I take the bluple LED out of the equation for now? I think that would make it a few degrees cooler in the tent, which I am leaving open during the day anyway, and using a fan to make it a little cooler at least until things cool off here a bit. Or should I go the other way and keep the extra light but cool my nute solution more aggressively?

Do you know how much heat your blurple adds?

Is a true 300w, or that’s what it claims?

Is hydro different? My whole grow has been above 80 degrees during the day. Holding temps of 86-87 for long periods before I switched lights. I still can’t get it below 82 during the day here…it’s HOT outside. My plants don’t care. I am in soil though.


I’ve never grown hydro, but I wouldn’t think 77 would be a problem. I grow outside and we’ve been having temps in the 90s/heat indexes in the 100s.

With it out, the temp dropped about 3 degrees in 2.5 hours.

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I don’t think you need it for veggie stage, I’d give yourself a break from cooling your nutes, and add it back once you flip to flowering. The choice as you know is up to you.

Do you have good exhaust? also, where are you exhausting to tent to?
I had to exhaust my tent out the window to help with my temps.
I was hitting 85+, i also have a portable AC that is also exhausted out the window.
I turned my lights on time to be on during the night to also help with keeping temps down.
I had to get a chiller to keep my water temps below 70 also.


Hey guys. I’m new… but i did discover this in my temp control endeavors. Leaf Surface Temperature with HPS, MH, CFL and LED Grow Lights – Black Dog LED
It pretty much says that we should be around 85 if you’re using led. Check it out.
Happy Growing!!

@Siksr I have a pretty good carbon filter and in-line fan setup. It creates negative pressure in the tent. I vent it about 6 feet away, albeit in the same room. I have another box fan in the room to keep the air stirred well so it does not materially raise the ambient room temperature.

what you want to do is exhaust it out a window or something.
the negative pressure is good.
what that will do is create negative pressure in the room, allowing fresh air to find its way into the room and then into the tent.
@NeoGroR taught me all this so he might be of better help with getting your temps down because he was of tremendous help when i was having really bad heat problems early on.

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Yeah man, you really should find a place to vent your exhaust. All you’re doing is recirculating air. You have old stale air.

Old air out, new air in.

As for your temps, ditch the blurple if you want, but add it back during flower, like Zee said.

And when it’s time to move on from the blurple, we’re here for you.

Blurple Buyer’s Support Group


gotta link the support group :joy:

The sf1000 pulls 100watts. No idea about your other blurple light. I’d use whichever pulls the most wattage.
It should be enough to veg a small plant. If it starts stretching you’ll know it’s not enough.

Is your exhaust vent pulling from the top of the tent?
Others are correct. Venting into the same small room is basically doing very little, especially with the tent open. Venting out a window would be a good consideration.

The SF1000 clearly pulls more wattage, event though I do not have a meter to check it.

I’m venting into a 750square foot basement with an open staircase to the first floor. There are no windows, just a door to the outside. I’m getting the exhaust about as far away from the tent as I can.

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Is this the correct light?

That’s not terrible. It’s a decent sized room…

I’d just use the the SF1000, much better spectrum than the blurple and probably runs cooler. Blurple probably blowing warm air everywhere.


@Drinkslinger - That’s the one. My blurple is 300w par equivalent, but probably draws about 30w

Which blurple? Maybe I can find it.

It does not have a brand name on the unit.