First of off it is not a septic tank; just a holding tank until it is dumped.
Next thing is the tank will not dump right unless it is part full, (no rush of water otherwise) so don't leave the valve open while on hook ups. Wait until the tank is say 3/4 full and then pull the valve to dump it, and start over.
Next thing is you don't need that nasty blue smelly stuff to stop the stink. Just use some laundry soap (two cups of liquid soap) after every dump. Once in a while, (every two dumps?) use some water softener ( a cup or two of powder) like "Calgon" to smooth the sides of the tank so it dumps better.
That blue stuff stinks worse than the "real" stink! :(
