Hello Jaysee: You make the most interesting post and I see you are willing to express your ideas. First I have to admit that I use two filters in my aquarium. its around 40 or 50 gals don’t know for sure the size. 1st filter is a 10 gal undergravel filter and the 2nd filter is fluval 305. Second I don’t test water parm at all meaning I do not track levels of ammonia, nitrite and nitrate. For me all levels are 0 ppm. I have tested the pH about a year ago and it is in the mid range 7.6. After reading some threads here at TFK I should try to start checking water hardness at sometime in the future.
Third I do not experience loss of live stock. Is it luck, poor grammar or do I have a wet thumb?
How would having 2 filters offer one bacteria an advantage?
the advantage is in colonization one bacteria type reproduces at a far greater rate than the other bacteria therefore the faster colonization by one would deprive the other access to real estate. The reasoning for the filters is due to the accumulation of organic carbon, which is a food source for heterotrophic bacteria. Autotrophic bacteria food source is nitrogen based not carbon.
How is the competition for surface area any different with 2 filters versus 1?
There is no difference with the exception there is more area to conquer for the fast reproducing bacteria
If autotrophic bacteria is in fact primarily in the substrate, how do the filters have any impact on that? And how is there competition for real estate
if one prefers the filter and the other the substrate? This is a very good point and the answer I will provide is that some heterotrophic bacteria (denitrifying) have the ability to reverse the nitrifying process creating ammonia from accumulated nitrate resulting in the shutting down the autotrophic bacteria colonies.
As to your point about theory and the realization of the theory in the world can not be disputed.
Caution: heterotrophic bacteria (denitrifying) food source is not carbon based but nitrogen based pointing to a weakness of my argument that suggest my opinion lacks validity.