Overnight temp

Well even if you don’t do anything to make temps drop. Temps drop because the light is off. In flower I’m just at around 25 degrees celsius with lights on and at night I’m around 22 degrees celsius because that’s my household ambient temperature. I’m also in winter here so I suppose you may have a different climate. I wouldn’t worry too much about making it a hard 18 degrees celsius at night, unless there’s a benefit to pushing lower temps at night that I’m not aware of. But I don’t air condition my grow space and I’m pulling 100 grams per plant in 5 gallon pots. But if you want to push 18 degrees at night. That’s completely acceptable for continued plant growth. Hope that answers your question. 🤙