Ouch, ya those are things to learn from really. I tried to simplify my water changes as much as possible. All my powerheads get shut off by one powerstrip, heater specifically set in my water mixing trash can, and a long enough tube to run from my DT to the sink when removing water, and that same tube is long enough to run from my trash can to my DT. Water changes take 5 min =)
But ya, its the small things that make the biggest impact in this hobby. Just gotta learn from your mistakes!
EDIT: Btw, some future tips:
I hope your not using "cold tap" from the sink. Tap water is horrible for fish, and especially corals. You're setting yourself up for failure by going that route. Use RO
If you ever run into an emergency where you have to cool down the tank fast, fill a plastic bag with ice and float it on the top of the water, fans also work nicely to cool temp fast.