What are you whining about!?!?! Try holding 100 degrees within .25 for 5 minutes on a push process! Seriously, set the thermostat to 68 degrees. if not get steel tempering pitchers (idk what you call them) and get hot water. Put them in and stir with thermometer until they reach 67. Take them out and they should reach 68.
Back before I had a temp. controlled JOBO I used to develop at room temp. and use a compensating equation. I could post the equation I used if you are interested. I got the equation by decoding the wheel in the Kodak darkroom dataguide.
Is this what I'm supposed to do? Then what? Wait until the chems even out with the ambient liquid temp until it cools down to 68? This could take hours.
No you fill the tub with water at your developing temperature and then you mix your chemicals using water from the tub and then you float your bottles in the tub. It will take 5 mins max and the tub should still be at developing temperature if it had enough water in it to start with. It takes much longer for a larger body of water to start changing temperature.
My darkroom is in the basement and the ambient temp is anywhere from 55 to 60 degrees F. I use a 50 watt aquarium heater set to 68 degrees. In an 11x14 tray with 2 liters of liquid, it takes about 15 minutes to heat up. I use a piece of foam board to cover the tray to help keep the heat in and prevent oxidation. When I do the full print, I take the heaters out because they have a little orange light (to indicate when it's on) that could fog the paper. The heater only cost around $20 a piece. I have two; one in the developer and one in the fixer. When developing film, I put a liter of developer in a graduated cylinder with the heater. When it gets to 68 degrees, I start developing immediatly. The temperature falls only about 1-2 degrees after a 13 minute developing time. I hope this info will help.
Just in case you're wondering, the developer in the tray is Ansco 130.