# Hang on Filter Diffusing Method



## Wood (Jul 27, 2006)

Hello all,

I kind of stumbled onto this by sheer luck. I am sure others have experienced the same. I have my CO2 line with the airstone positioned on the bottom of my 10 gallon tank in between the filter intake and outflow. I have a topfin hang on filter, like the one pictured below.










As the CO2 bubbles approach the surface, the current takes them straight to the outflow. Here is the interested thing, most of the time they don't get thrown out and around on the surface and eventually pop, they actually get "sucked" underneath the outflowing water and stay there, constantly being spun underneath the outflow. I watch the bubbles and they get smaller really fast. It only seems to work though with medium sized bubbles, about half inch in diameter. Since I have a very small "bell diffuser" over the airstone, the CO2 builds more than it diffuses in the bell, so only large bubbles come out. I fill the water to about halfway up the outflow slide of the hang on filter. That way there is plenty of room for the bubbles to get stuck underneath and spun by the constant stream of outgoing water and the slide acts as a backstop to basically trap the CO2 bubble, allowing a lot of water to flow over the bubble. I will definitely research this some more, and perhaps I can give us "hang on filter" guys an easy way to diffuse CO2. Maybe running the CO2 line directly to the point where the bubbles will be trapped???

Please try to imagine what I am talking about. It is hard to explain and I am sure that I have confused some. Please give me some input, or any other experiences you may have had with this type of situation. My plants are pearling A LOT.


----------



## Blacksunshine (Aug 11, 2006)

Its a good idea however personally I'd ditch the bell all toghether. I have my CO2 piped directly into the intake of my AC30 (I think) and it takes the bubbles directly into the watercollum chops them up at the impeller and then dumps the saturated water back into the tank. 
The only thing with this kind of a set up is you have to make sure that your water level is always as high as possible as well you want to set the filter on the lowest (if adjustable) setting to minimize surface agatation. 
Even at low light this resulted in some good pearling in my plants.


----------

