Re: Over-filteration and algae

Hi KB,

> 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. 

How do you get the powerhead to blow downwards? Did you construct a
flow redirection vane of some type? The smaller of my two powerheads
has such a built-in vane which I direct downwards. It has very little
surface current but the underwater current is still quite strong.
The fish like to sit in this current and wait for particles of food
to be swept toward them. I think it is a natural type of feeding

> 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. 

Yes, I have seen brush algae with less CO2. I'm very curious about
this over-filtration idea; could you tell us more? What is the cause of
it? Maybe over vigorous filtration could encourage blue-green algae
which is using gaseous Nitrogen. Another thought is that strong
currents might disturb bottom material (mulm) and cause mixing of
nutrients being slowly released by decay. I think it is better to have
the nutrients inside the substrate rather than in the water for the
algae to use. Those floating plants which I have never seem to have
a shortage of nutrients and grow like crazy with strong light.

> 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. 

I'd be interested in reading this compilation. For informal discussion
such as this, I think it would be ok to place the quoted paragraphs
in quotation marks and give the source. I'm not sure how copyright laws
apply to the internet especially in overseas countries. Perhaps someone
can advise us.

I've noticed greater CO2 loss when the water level is low and my trickle
filters are creating a waterfall. To counter this, I attached a clear
piece of plastic with silicone so that the return water flow rides
smoothly down this. The plastic is just like that for overhead 
transparency or report covers. This really reduces turbulence and makes
the filter very quiet too. The other benefit is that the water flow
does not push my floating plants around so much, or cause them to shoot
under water where they can get caught under the leaves of other plants.