I don't consider wet dry, any better than submerged media (at least in my tanks, I haven't noticed any difference one over the other, although I have used both).
Once enough beneficial bacteria have populated the existing media to use the ammonia produced by the stock, more media, or another ammonia consuming concept is redundant.
To me, adding something totally different concept that focusses on reduction of nitrate like a planted sump, algae scrubber, or something that removes dissolved organic carbon directly from the water column, or exports nitrate precursors (such as fractionation) would be my idea of approaching ultimate filtration.
About 3 weeks ago, I removed two sumps (one mostly wet dry, one with mostly submerged media), which contained in total, about 2/3 of my biological media, and replaced the 2 sumps with a 24" x 6" x 21" area of a newly set up, 125 gallon tank (it is inline with a a 3 year running 180 gal). So now a total of about 300 gallons
I placed about 1/3 of the "old media" between a new 2" Matten (Porrett) foam block, and also added a large Papyrus plant to the end of the 125.
I have been testing, ammonia, nitrate, and pH every other day to watch for any spikes or significant changes due to the changes in filtration.
None have occurred, no ammonia spike (normally no readable amount), no nitrate spike (its usually less than 5 ppm), and pH has not deviated from its norm at this time of year, of about 8.2.
My normal water change routine is about 30%to 40% every other day. A Link to the change below
Used 125 gal
The stock has also remained the same (with the exception of a pair of Andinoacara in the 180 now guarding about 50 free swimmers)
