Canadian Fish I'm glad you are enjoying your Python hose on the tanks.... sure beats hauling buckets!! A few tips...I have used one for years!
Once you have the hose connected and the siphon going, you can actually turn off the water and the siphon will continue slowly allowing you to gravel clean (carefully around the plants or in areas with none)
Turn off the valve and move on to the next tank. You can do all the tanks at once and will save a bit of water this way when refilling.
check the temperature of your tank(s). Hopefully they are very close to each other, makes it easier.
Determine the amount of water removed and add the appropriate amount of De-chlor directly to the tank so it is there ready when the new water is pumped in. It's instant, no need to wait, works fine that way.
Lock the shut off at the tank and return to the sink. Change the setting so the water flows thru the valve and set your temperature of the NEW water here. I use a marg container under the valve to collect water and take my time to stabilize the temp, thermometers are slow moving. Make the flow not too hard, not too slow but find your temp at a reasonable flow. You can come back and recheck it by opening the valve at the sink temporarily.
Lock the valve to send the new water to the tank.
Run back to your tank (water pressure in hose) and open the hose valve. Do not leave the room. Once you overflow one... you will only do it once! LOL. NO it is not funny!
It is ok if the temperature is 1-2 degrees max lower than your tank... it is like a refreshing rain in the wild.
After, I hang the hose folded over in half over the bar in the shower for the rest of the day to allow it to drain and dry. Hoses can get black inside if left wet.
As to more tanks found on Kijiji.... they are starting a rehab in your area for addiction. I think you should join.