# Flocculation



## niko (Jan 28, 2004)

*Flocculation and biomedia*

For the people that don't know flocculation is the bundling together of small particles into larger particles. For aquarium purposes that means that fine dirt can form larger clumps and either settle or be retained by the filter.









The way fine particles start to stick together in a planted aquarium is through the CO2 bubbles. I heard about that for the first time when reading about ADA's system. ADA normally places the CO2 diffuser on the opposite side of the filter outflow. The filter shoots water close to the surface, then this stream hits the opposite glass and starts to move down and to the sides. The CO2 bubbles raise from the diffuser attached on the opposite glass. Basically the water hits the bubbles from above while they are trying to float up. This leads to a good diffusion but also whatever fine dirt is floating in the water gets stuck to the bubbles. When close enough the dirt particles start to stick together. The bubble bursts and disappears but the new, larger, dirt particle stays and it it either settles to the bottom or gets trapped in the filter:










That is all in theory. How well flocculation works you your tank is another story. Does it really work anyway? That's why I wrote this post (which is nothing new). I had a recent experience and I am quite sure that flocculation cleared up the tank water. Here's how it went:

I have a 180 gallon tank with no plants. Just water, inert gravel, and a big shcool of wild tetras. The filters have only Lava Rock. No mechanical filtration. Some time ago I thought that biofiltration will take care of all the dirt in the tank if you use the right kind of media and good flow. After all that is what ADA does. But that is not true if you forget to look at your tank as a system. My mistake was that I took one part of the ADA system and expected it to work. So my tank is doing ok, but I always have tiny suspended particles floating everywhere. The water is crystal clear but these particles never disappear. It has been like that for 3 months now. Water changes do not change anything.

About a week ago I added a powerhead with a CO2 supply stuck in it. A big cloud of tiny bubbles is now being sucked by the filter outflow and moved to the other side of the tank. That is not the best way to distribute CO2 but I did not want the powerhead on the opposite side of the filter outflows. It is ugly.

So on day 3 after setting up the CO2 I notice that the water is now crystal clear. There is no way the fine dirt would disappear just because. All I see are the tiny CO2 bubbles now floating in the crystal clear water. I have no explanation where the fine dirt went. The only thing that comes to mind is what I described above - the CO2 bubbles flocculate the fine dirt and it settles. It could be that the Lava Rock actually retains it now.

My Lava Rock is pretty coarse. ADA uses a much finer porous substrate (Pumice) which you can also get dirt cheap from Ebay. It is used in bonsai. I got a box of Pumice the size of ADA's. The original ADA Pumice is much more uniform than what I got. But the idea of using that size Pumice is that it actually retains fine particles. ADA filters actualy clog pretty quickly. So what you see in an ADA filter is only biomedia but that biomedia is also a mechanical media.

Ebay pumice:









ADA biomedia (Pumice):









And this is how ADA sets up the filter in the first 1-3 months of the tank setup. Initially the filter has some Active Carbon in it (the top layer that you see on the picture). Later the entire bag is filled with Pumice. Note that at no point ADA uses any mechanical filtration. On this picture you can see a thin layer of coconut bark. It has some mecanical filtration properties but really it is there to support the Pumice and not much more (the bottom, brown layer):









Because the media clogs up pretty quickly ADA uses a pressure rated pump on all their filter. These pumps are designed to keep the filter flow at the same level even if the filter is mildly clogged. What you get is time to clean the filter - it does not reduce its flow as soon as the media starts to get dirty. The pressure rated pump also keeps the biofilter alive - with reduced flow the filter can actually make Ammonia instead of eating Ammonia. So please look at the ADA filters a bit different now. They are indeed not only made well but made with a lot of thought.

In any case - if you feel like it experiment with flocculation in your tank. I always thought that the effect would be minimal but I cannot believe what I'm seeing in my tank.


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## Yo-han (Oct 15, 2010)

A good example of flocculation is a product like Easy life liquid filter medium, which I believe is basically grinded zeolite. All small particles attach to it making a big particle which is filtered out easier. I've read this about CO2 bubbles/mist before, and it seems to work but I still prefer my out of sight 100% dissolving CO2 reactor. But it might add to the crystal clear water...

PS. your inbox is full niko!


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## niko (Jan 28, 2004)

It's good now.


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