The Planted Tank Forum - View Single Post - Mini CO2 reactor in an Aquaclear HOB filter v1.3b (shown on a Fluval Edge)
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post #1 of (permalink) Old 03-20-2010, 05:01 AM Thread Starter
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Join Date: Nov 2009
Location: Santa Monica, CA
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Mini CO2 reactor in an Aquaclear HOB filter v1.3b (shown on a Fluval Edge)

I think this has been discussed in a few threads but not really documented clearly, so I figured a DIY write-up could be helpful. I'm currently using this method to inject CO2 on a Fluval Edge (which comes with an AC20 / Mini HOB), but it should work on any AquaClear HOB. In contrast to bubbling the CO2 directly into the filter intake, this configuration keeps the airline out of the tank and avoids impeller gurgling noises.

Inside the filter, there is an impeller cover. Pull this out, noting the hole that is used to expel air when priming the filter.

The plan is to insert airline through the hole in the impeller cover and attach a diffuser to the other end. I used a broken chopstick piece. Another alternative is the Lee's discard-a-stone "slim", seen here. The space is pretty constrained so options are limited.

The airline and diffuser fit through the impeller cover like this:

Now, reinsert the impeller cover. You want the diffuser to stick out like injects into a narrow column of water between the filter basket and the impeller motor housing

Note: the hole that we plugged up with airline tubing was there so air could escape while priming the filter. So we need a different way to expel the air trapped below the impeller cover and prime the filter. Solution: pull the filter basket tab in this direction while the filter is priming:

Its like a mini-CO2 reactor. Bubbles get jostled around the downflow and anything that is undissolved is trapped below the sponge. At least for me, the CO2 diffuses at a sufficient rate that a big CO2 bubble doesn't form.

6g Fluval Edge journal
45g ADA 90p (early days)
2g Do!Aqua cube (unplanted for now)

Edge Tuning: 26W lighting conversion - concealed pressurized CO2 - HOB CO2 injection - nano HOB heater - lunar lights

Last edited by tuonor; 03-30-2010 at 10:17 PM.
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