ehiem cannister
any cannister filter usually runs with a lot of flow as u mentioned it started out with, if it drops u r generaly dealing with air in the cannister and the flow will never reach full flow with even a little bit of air in there. when i run into this i check for sporadic air bubbles coming out of the return hose, and i can generaly hear an occasional "slurge?" of air within the cannister getting sucked out. In my experience I have found that when you first set up a cannister filter the hoses and connections are all room temp and go together fairly easily and everything works fine but as the weight of the hoses sets in and the heater does its job the hoses and water weight works with gravity and things start to settle allowing sealed connections to break lose just enough to let some air in. this air induction only works on the intake hose. u can also get the same thing with the lid to cannister o ring. I always use a little vaseline on the seals and hose connections and no longer have the problem. also, when running i cant hear my eheim 2217 run, its the one where its just an empty bucket that u stuff floss and bio media or for that matter ,whatever suits ur fancy as oposed to the little chambered ones that have the slide in cartriges and channels cause to me that is just about the same as a HOB filter that has no easy access.I used to run fluvals but a couple of times a year I would have to replace the impeller, when I switched to eheim I decided to save myself a trip to fosters and smith and bought an impeller so when the day came for me to replace it , it would already be on my shelf, the only problem I can dig up is that 5 years ago I went with an eheim and I havent had to use the replacement impeller..............Oh yeah, its almost impossible to have trouble with repriming the filter if you go with the quick disconnect/shutoff valves. jim
