Cheapest, simplest way of managing temps in a single DWC bucket

Lockdown has its benefits... keeping water between 18.5 - 20c (64.7-68f). At the moment the grow tent is 30c (86f), which means I'm taking 2l out and adding 2l in 4 times a day! RH is stable at 55%, so I've got everything dialled in. Currently at 720ppm (1.4EC) in the nutrient solution - just entered week 6.

I managed to turn LST into VERY high stress training last week, by lifting the bucket lid when I had everything tied down. I was literally left with a stump about a week ago, but thanks to the established roots it all came back within a week. I've been able to keep everything low and I reckon I'll have 16 'tops' by the time the week is out... that is, if I can stop being so heavy-handed when tying down! Round 2 LST and I snapped one stem and half snapped another (hence the plastic wrap trying to graft the half snapped top back together).

I only tied everything back down again yesterday, hence it still looking a bit sad. I've removed a few fan leaves today which were blocking light from the lower shoots I'm trying to encourage up to the canopy level.

The photo of the stump is from 8 days ago... others I took just now

I know nobody asked, but here's my little tent. TSW 2000, 1 gallon humidifier, fan clipped on the side of the light pointing directly at the plant. AC Infinity T4 fan, nice big carbon filter... radiator is just to ensure night temps don't drop below 23c. I elevated it to ensure it wasn't just heating the nutrient solution

Not bad! If it was me, I'd switch lights for flower tho.

If I had lights for flower, I would... this has got 740nm diodes and 660nm diodes too? Thought red spectrum was better for flower?

Read many reviews saying it's suitable for both phases... and I can get ppfd to 1,000 across the whole footprint of the tent with 16" distance when the time's right?

I'm not saying you can't or you won't grow good flower. The light energy is what determines yield mostly. Nothing contributes more to yield. 1000 ppfd? I barely get over that with my timber in a 3x3 at 18". Though I'm not real familiar with your model light. If you're getting 1000 ppfd from it then it'll do just fine. Red is better in flower but those 2 diodes i would use as a supplement to full spectrum white. I believe those 2 reds would work for Emerson effect but not exactly sure on that. You might wanna look it up.

It's the Mars Hydro TSW 2000...

My girls don't seem to mind