Over-filteration and algae


I was compiling information on the subject of Algae from various books, 
magazine articles and r.a FAQ. Dennerle stressed the importance of 
biological filteration in conjunction with mechanical one. We must not 
have over-filteration or too-powerful filter for our tank size or the 
algae will set in. I was able to relate this to my current experience 
whereby I started to use powerhead as my CO2 reactor. It spray tiny 
bubbles in a powerful current across the tank. After a couple of months 
red brush algae start growing on the edge of broad amazon sword leaves 
and lots of other green algae on the leaves' surface. Previously the 
brush algae grows only on my slow growing Aglaodorum in minutes 
quantity. On the other hand, I've also noticed that this method of CO2 
injection is not efficient as the pH drop is not much. Due to this two 
change I've now change the powerhead setup in such a way that the outlet 
will not blow all the way across the tank resulting in better efficiency 
as my pH drop all the way to 6. 

What do you guys think? Algae invasion due to over-filteration or drop 
in CO2 level? I have yet to determine the effectiveness of this new 
change. It has just been a few days. 

Next, I'll partition my cannister filter to follow Dennerle's method in 
having both mechanical and biological filteration simultaneously. If 
there are demand for my compilation, I'm willing to post it to AFD. It 
contains a lot of copyrighted materials though.