Dry ice in hydro

Has anyone ever experimented with using Dry Ice *compressed co2 gas* in their reservior? I live in a fairly hot area and have trouble keeping my water temps stable. I use sterilized icepacks for coolers as well as modified frozen water bottles every few hours to keep my temps under control. If I dont change them out after about 6 hours my water will be 83*f+ ... Being that Dry Ice is purely compressed co2 gas I wanted to use it in my water to a) flash down temps and keep under control ... as well as b) deposit co2 into my water which is aerated by an ultrasonic fogger, creating a nute mist for roots to bask in ... The only thing Im skeptical about is *and correct me if Im wrong* that co2 lowers the dissolved oxygen levels in the water. Plz let me know what you think about using Dry Ice in my res ...

p.s. a local grow shop employee told me that it was toxic ... yes its toxic to humans but is it still toxic to plants in its dissolved form? Idk ...

I think the CO2 changes state from the solid to the gas. They need CO2 but it's the topside that needs it rather than the roots as I understand it; the roots need O2, the leaves need CO2. Also, I think the roots would be fried if they touched the dry ice.

I do see your point. In humans co2 is an oxygen inhibitor so i guess it would deplete oxygen in the air if the mist was full of co2 causing the roots to suffocate. Ive been playing with the idea of taking my old Mini Fridge *got a new one for xmas* and removing the frezing coil from the freezer portion. I dont believe it is strong enough to freeze the water if I put it on the floor and set the rez on top of it, but I do expect it would keep my water ice cold. From my experiences colder water has a higher DO level which is good, but can the water be too cold? Ive ran it as cold as 50*f before and never saw a noticable problem. assuming the temp doesnt drop too quickly and shock the plants.

oh man - 83F is hot for the reservoir... i had to give up DWC because i couldnt keep the temps under control and i didnt want to buy a chiller (which would cost about $500, for a "real" one)... i tried 2L bottles filled with antifreeze, home made chillers, and just about everything else i could think of....

i tried to make a mini-fridge chiller... i couldnt get it to work... i tried 2 ways:

1... i just drilled 2 holes in each side of it, and put some tubing into the fridge, i put a big bowl of water in the fridge, and ran as much tubing through it as i could, in theory, the water going through the tubes would be chilled as it was pumped 10' through tubes in the bowl of chilled water... that was annoying because the water evaporated and had to be replaced all of the time - and it didnt really chill much... it did shave a couple degrees off the res temps, but nowhere near what a real chiller would.

the second way i tried, i completely dismantled the fridge, i ripped out the copper coils that are wrapped all around the inside of the fridge, and they are insulated with foam, i took out the plate where the gas is expanded and freezes.... i tried to drop that feezing plate into the res, but then i saw it wasnt freezing... i found a hole in the copper tubing, fixed it, and attached a schrader valve to the mini fridge compressor, brazed it on - refilled the system, rigged it up and it took off about 8 degrees...

my advice: get a real chiller if you want to do DWC, making one is a pain in the ass, and you also have to compensate for the heat of the water pump running 24/7...

part of the problem are the air pumps, which are pumping room temp air into the containers all of the time, and depending on your room temp, this will change the water temp pretty quickly...

in the DWC system you wanna keep your roots at 65-70F ideally... anything over 72 will grow aglae like a mofo, and cause root rot - where the roots turn brown and mushy... you can hardly recover from that...

oh yeah - about the dry ice... i've added that into the room to melt infront of the circulation fan before, but i've never put it in the res... that would choke out the oxygen for sure, you want lots of o2 in there... the dry ice will work, but its no good for chilling the reservoir, only adding co2 to the room for about 1 day