whats the name of the doser that DOES have issues (so the rest of us can stay away from them)
In Ontario we are organizing a group buy for OEM peri pumps. They look exactly like the units in the Bubble Magus and GHL / Fauna Marine Dosers.
They are going to be $20-$25 a pop but you will need your own power supply (12v dc adapter is about $5-$10) and a timer (or a reef controller) If you are interested visit this thread;
http://www.thefragtank.ca/forum/index.php?topic=940.0