What fish? Planted tank? Pictures?

 

I like my magnum 350 but it's not really made for biological filtration as much as particle filtration but they do have a bio wheel attachment now that would make a good addition for the bio load. I only use mine every so often to filter out fine particles now. I Used to have it on my 55 gal with the special canister insert that allows for bio filter medium. But I also had 2 power heads and a large whisper filter.
I have a wet/dry sump now for my 150gal FW and really like it so far. I use an 1800 gph pump with it. But I like the idea of the emperor filters with the bio wheel. They have 2 sides each with double filtration on both sides. Pretty neat.

 

If you are using C02 then your tank is probably doing well with plants. Obviously your tank is well established with the fish you are housing, I looked in your profile. So your tank will be its own biological filter with plants, etc housing many of the beneficial bacteria. If I owned your filter, the only reason I would change it would be if it is noisy, then I would go to the smallest Eheim canister system and use it. Eheim has been around for a long time, some members here have been using their Eheim canister filter for 15 years or more; its German made.

An overview of the Eheim Filter Range

 

I also swear by Eheim of any of my larger tanks for years now, love it, won't ever get any other brand canister I use these Ehiem Plus Series Filters, Eheim Canister Filters | Pet Solutions

However for that size tank, I'd pers get a Internal filter; I recently got these for my 45g Cascade Internal Filters, Internal Filters | Pet Solutions and really enjoy them for several reasons...Unlike most Internals these have adequate room for bio media and sponges, they're real powerful compared to other internals (I bought the 600 Model for the 45g but would get the smaller version next time around, on its lowest setting it too powerful for a 45g), it is superst quiet no noise involved. I can however not comment on years of experience like on the Eheims, but looks well built to me and works great since I added it and I just am hiding it away behind driftwood & plants (See pictures in the aquarium log "New 45g).
Eheim also offers a internal called 'Aquaball' which I used before in smaller set ups, being the Eheim fan I am, but it does NOT offer the space for filter medias like the Cascade does.

 

Thanks for the imput, i'm going to do some looking around with the ideas ya'll have given me. I'll post something about my new filter when/if i get it. I had not considered an internal filter before, but it looks like i have plenty of options. Thanks again

 

In a heavily stocked tank the plants will do little for filtration. Planted tanks only make a significant impact on a very lightly stocked tank.

If you introduce CO2 via liquid ferts then a good hang on back like a Penguin will do just fine. If you're using gaseous CO2 or no CO2 injection at all then you want a canister so you can avoid surface turbulence which drives off CO2 in favor of O2.

 

from what i have read on a fresh water aquarium the filter system should turn the tank at least 4 times per hour.So if you have a 20 gal tank your filter should move at least 80 gph but you also have to consider the filter specs are given with no restrictions on the filter.Just because it says 350gph does not mean thats what it does when you add the lift and pushing water through the filter media, i figure that my magnum 350 is doing probably closer to 200 gph rather then 350 gph as they advertise.My opinion is you can never over filter a tank the more filtration the better for the fish.You should really consider a under the tank wet/dry sump filter they are a easy do it yourself project and less expensive then canister filters.Plus do way more filtration and add water volume to your system.I am getting ready to set up a 29 g as a breeder tank and i am going to use a sump and my plan is to get it some where in the rang of 300 gph filtration because i need it to be super clean.Just use a 10 or 20 g tank and build your own sump there are plenty of diy instructions on the web that will help a bunch..

actually here is a good diy site i stumbled across a few days ago..
Do It Yourself


good luck...