The wet/dry system is actually very good for ammonia and other toxin break down because the system adds more oxygen to your water than a canister. They are really good at bological filtration because of this increase in oxygen, whiuch is used by th ebeneficial bacteria to reproduce. However, having the canister filter hurt. You can use it to stur up dead zones in the tank, more surface tension, andd a stronger current in your tank. I've tried to do a little more filtration than what is needed.
darknirvana, you have some confusion over what some of these terms mean, or you are just plain using them wrong.
Firstly, when I am sure that the bacteria does use oxygen to reproduce, the main reason they need oxygen is because that is what they need to sustain life.
Look at the what the ammonia-consuming bacteria do. They convert ammonia, chemical formula of NH4 (N for nitrogen, H for hydrogen) to nitrite, chemical formula of NO2- (O for oxygen). They have to have oxygen to convert the ammonia to nitrite because ammonia has not oxygen in it's chemical formula and nitrite does. This isn't just to reproduce -- this is simply to live. This is a process called oxidation, and the bacteria are commonly called "ammonia oxidizing bacteria" (AOB). This oxidation reaction is the bacteria's main source of energy.
The nitrite consuming bacteria do exactly the same thing. They excrete nitrate, chemical formula NO3-, as their waste. They also have to have oxygen to live, because oxidizing nitrite into nitrate is the "nitrite oxidizing bacteria's" (NOB) main source of energy just like the AOB. Nitrate has one more oxygen atom in its formula than nitrite, so it has to get that from the air.
Secondly, the surface tension of the water is pretty much independent of how much or how little filtering is going on. It is much more a function of what oils and organic compounds are dissolved in the water. Unless lots of nitrate builds up,it usually won't have a large effect on the surface tension at all. In fact, the concentrations of most stuff in a fish tank are so low that they won't have an effect on the surface tension. I think that you might be thinking of a different concept, because the way you've used the phrase surface tension doesn't make much sense at all. See
http
/en.wikipedia.org/wiki/Surface_tension
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Nick, there is no such thing as "too much filtration." Biologically, the number of bacteria grow in response the rate of production of waste from your fish. Adding another filter to your tank doesn't change the number of bacteria -- it may change where they are located as bacteria move into your new filter, that will be at the expense of the number in the old filter. If you don't change the number of fish, or their feeding habits, then you won't change their rate of ammonia production, so there will still be the same number of bacteria. The number of bacteria doesn't care how many machines you have moving water around, 1, 2, 10 ... doesn't matter to the bacteria.
However, the fish might. Depending on your fish, they may not like having too many currents in their tank. If the fish are from slow moving streams or ponds, they definitely won't like strong currents. If they are from fast moving streams or rivers, however, they might really like some additional current. This is where researching your fish pays off.
If you want your water "crystal clear" (as an aside, I don't know why you'd really want that -- water is nature isn't crystal clear and crystal clear water doesn't necessarily correspond to a healthy tank -- but to each their own) you'd probably want to get a micron filter or diatom filter or something like that. Maybe using activated carbon, or zeolite, too. A combination of mechanical/chemical filtration will polish the water.
