Wow...your question is very similar to my situation. I too had a Emperor 400 on my 55gal tank. Although it did its job very well, I didn't like it for the very reason that you mentioned. I also didn't like it because the cartridges were very expensive. One other thing that I didn't like was the bio wheels seem to create thousands of tiny micro bubbles that would float around in the tank. This may be benifcial, but I found them unsightly.
Also you are right. Except for certain situations (such as removing medications
), carbon should not be used in a planted tank. As you say, the carbon will remove certain trace elements that are benificial to your plants.
Well.....I got rid of the Emperor filter, and bought a ViaAqua 300 canister filter form Dr Foster & Smith's Pet Warehouse for just 59 dollars! The 300 is suppose to be for 20-40 gal tanks, but yet it has room for 3 liters of media and has a 210 gph flow rate. Thats almost recycling my tanks water 4 times per hour, so I figured it was big enough. (they do make larger models for a few dallors more
I've only had this filter for a month and a half, but so far, I'm extremely pleased with it. My only slight critisim is the primming can be a little tricky, and the quick release connectors could have been designed a little better. But at that price, its hard to quibble.
As far the Eheim Pro II, as it turns out, I may be purchasing one of these too. I'm in the process of setting up 125 gal show tank, and I want everything to be the best. From everything I've read, Eheim is the Cadilac of cannister filters and last for ever.
I don't know where you plan to buy your filter, but I highly recomend the above mentioned catalog retailer. You can order a free catalog here.
You can also order on line, but the catalog has more product choices. I've ordered from them many times, and have never been disappointed in their service. Also, their prices will always be cheaper than your local pet store, even when you include shipping.
By the way, their price for the Eheim Pro II 2028 with free media is $215.99. (2026 $165.99
) I will say, Big Al's catalog has it for $199.00, but I've never done business with them.
Anyway, I hope this post will be of help to you.