fluval 404 as a diffuser - The Planted Tank Forum
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post #1 of 7 (permalink) Old 01-16-2004, 04:43 PM Thread Starter
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Im using a fluval 404 as a diffuser for my 150 g tank my ph is 7.3 and my k.h is 1.5 , but the ph isnt dropping , im putting abouut 30 bubbles per minute into my tank from my bottle any ideas...is the gas escaping from the fluval ????
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post #2 of 7 (permalink) Old 01-16-2004, 06:02 PM
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Are you just letting the air bubbles get sucked into the intake? Or is the Fluval pushing a reactor? If you inject gas into a top-mounted impeller canister filter (like the Fluval), the gases can collect in the magnet chamber, causing it to run "dry" and overheat.
In spite of the danger of damaging your filter, I'm surprised you're able to diffuse the CO2 at all through your Fluval. As long as you don't see CO2 come out the other end of a CO2 reactor, you know it is dissolving into the water (or collecting in a chamber, to dissolve later). With a low KH like 1.5dKH, I would worry that the pH would drop TOO quickly.
How long have you been running CO2 into the tank?

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post #3 of 7 (permalink) Old 01-16-2004, 07:00 PM
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What I have gathered from playing around with canister filters as reactor chambers, injecting CO2 into the inlet will not lead to accumulation of air in the magnet chamber. At least in the case of Filstars (I am assuming the Fluvals use a similar design). The CO2 enters the canister housing, and would have to float down to the bottom, pass through all filter media, and then collect in the impeller chamber. Any CO2 reaching the impeller would be immediately pushed out through the tubing into the tank.
Instead, it remains on the top in the outer housing, and is dissolved there. The only negative effect I could see was that the noise level went up, due to the water rushing in and mixing with the CO2.
This principle is often used with powerheads sucking the bubbles in and smashing them up. Here, there is a danger of air/CO2 collecting in the impeller chamber in the case of power outages, which might dry-run the power head. Not so with canister filters.

So I think the bubbles are dissolving. 150 gallons is a lot of water... Is the Fluval the only filter? Or are there others that possibly create surface agitation? Perhaps you only have to increase the bubble count, very slowly, while monitoring pH.
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post #4 of 7 (permalink) Old 01-16-2004, 07:57 PM
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So Wasserpest, I can just run my C02 into my canister intake without any hazards..except for the audible noise?
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post #5 of 7 (permalink) Old 01-16-2004, 08:08 PM
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That is my experience.

Having said that... I use an external reactor on the outlet side now, both because of the noise I got when bubbling into the inlet, and to reduce the fine oxygen bubbles coming out of the filter every afternoon.
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post #6 of 7 (permalink) Old 01-17-2004, 04:43 AM Thread Starter
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i run 2 fluvals , 1 each side and yes co2 into the intake, with a little surface aggitation from 1 fluval spray bar the othere in the tank water. so IYO it will work just increase the co2?????
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post #7 of 7 (permalink) Old 01-17-2004, 01:53 PM
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I use 2) Eheim 2213 canisters on my tank, with one being the defuser, I cant find a better way to desolve c02, and even if quote if it did run dry and fry the impeller, its only $10, I cant build or buy a better defuser for that, I adjust c02 levels by adjusting spraybar for more or less surface movement, I did a test, first I let it run for awhile with spraybar about 2 to 3 inches below surface pointing up creating surface movement, pH would hover around 7/7.2
I then lowered a bit more and pointed spraybar to back glass, within a day the pH dropped to 6.4/6.6
Raise and point back to surface would rise back to 7-ish etc

So, in my estimation, canister with media is absolutly the best defuser by far.
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