I have never had a Eheim 2217, and I see it is rated at 264gph w/media, so in the 75g it is turning over the entire volume of the tank about 3.5 times a hour! I am wonder how much the flow is restricted with different kinds of media you can put in a Eheim of that style? I don't know what the flow rate is on the Fluval C4 hob you have, but I bet it isn't enough! With the small bioload you have I would say you have enough filtration, but not enough circulation. Normal power heads have to focused of a output, so I would either put a spray bar on the Maxi-Jet 600, or get a circulation kit for it (if you can for the model you have) so it will spread the flow out! By circulation kit I am talking about the newer MJ power heads can be switched over from a power head, circulating, and another setup too. I have seen them packaged with all 3 options or you can buy the kit to change the output type! IF the MJ you have won't switch over, then I would build a spray bar for it, so you don't have to spend to much more on it, or buy 1 or more of the Circulation style pumps, and forget about it!
If you plan on adding more fish then I would go for a second canister filter, and be done with it!
I hope this helps Ya out some!
I have 2 Fluval 205 canister filters on my 55g, and they are just about right! They put out about 206gph. So I am turning over the water about 7.5 times each hour. But I have a Co2 Reactor on one of them so I know it is a bit slower! I am going to build spraybars for both outputs to keep everything stirred up, because with just the 2 "normal" outputs I have dead spots still, even with that much water flowing!
Last edited by BoxxerBoyDrew; 12-14-2012 at 08:48 AM.
Reason: added info