Which type of biofilter has better performance in the removal of ammonia from the water, a submerged biofilter or a Wet/Dry Trickle biofilter? I have a wet/dry trickle filter in my 125 Saltwater and was looking at building a new stand and putting a sump in my 70 Freshwater, solely for the purpose of increasing my volume to provide more breathing space for my fish and to get rid of in tank filters, heaters, thermometers, etc. that I don't want to look at anymore. I know that the submerged biofilter will give me a larger volume of water in my sump, but don't want to sacrifice quality of the filtration process by not having the biomedia exposed to the air. I've never had a sump on any of my freshwater tanks(nor a submerged biofilter) and thought that I would give it a try.

Also, in general, what would be the requirements for the surface area (sq. ft.) of bio material per gallon of water(what sq. ft would i need for 70gal FW)? Are the requirements different for the submerged and wet/dry types?

Thanks in advance and glad to have joined this forum. Alot of interesting stuff here.

By submerged do you mean an in-tank filter? I would only consider one of those for a really small tank, but that is just my opinion. As far as removal of ammonia and nitrite, no filter will outperform a wet/dry. Removes them about 50% faster. Not sure on the bio material requirements, but you could always look up some wet/dry filters and get their specs and try to match what they use.

By "submerged" I mean where the biomaterial in the sump is completely underwater. There is no trickling effect. The water just flows over/through everything. Here is a basic sketch of what I believe it would look like. This way if the power goes out the biomaterial will always remain underwater. The water coming in will trickle through the filters(course,fine) which will be at the highest point above the water level. then a series of "waterfalls that the water will flow through the various stages. then finally into an empty chamber where it gets pumped out. The proportions may need to be adjusted, but the sump will be able to handle any volume of water than would come out of the aquarium during a power outage. Also, the picture is wrong, the water level after the bioballs would be lower(at same level as after carbon, before empty chamber). The walls would be siliconed to the side and/or bottom where needed. Additional media could also be inserted between bioballs and carbon, with addition of another piece of eggcrate. And Sinking type bioballs would need to be used. Airstones could also be placed under the biomedia to add more oxygen to the equation. Any thoughts?

if your using bio balls there better used as a wet dry filter as more effiecent that way as there not designed to be submersed in water.
alfragog can be used but clogs over time ,sintered glass rings,sponge,jap matt or moving bed media like Kladness K1 or similar if aerated this is highly efficient