I've been using one of their pumps for about a year now. I use it for kalk/makeup on an 80g tank. It has performed really well and since it's old medical equipment I think it may last forever. The only thing you have to watch is make sure the bubble in the tubing set sits high enough so you don't get a free flow conditon which shuts the pump off. Also make sure you get extra tubing for the part that actually is pumping.
I mix my kalk in a square 5 gal plastic water jug. I used a piece of rigid tubing to go down into the jug till it's about 1.5" from the bottom. The pump has no problem keeping up with my evaporation. Overall I am really pleased with it.
