Fluval canister filter as a diffuser, works but its strange

[b4tn]

All I did was take the pressurized CO2 line and push it into the inlet inside the tank. The filter sucks up the bubbles and thats it. I was expecting some sort of bubble output but noting comes out but water. The filter is not stalling burping or anything. Strange I was expecting to be able to hear the baubles get all churned up inside the filter and was also expecting to see some sort of output. On another note, It takes very little CO2 to drop the levels! and it can drop real fast if not paying attention.

I was reluctant to do this at first but I read somewhere that fluval canister filters where not at risk of running dry from CO2 being injected so I figured I would give it a try. And it works!

 

[malkore]

you shouldn't see anything on the return...so that's normal.
i inject into my aquaclear HOB, and i hear each bubble hit, but it's a silent filter. if the fluval motor can be heard its probably masking the sound of hte bubble breaking on the impeller.

the only canister's not at risk for an airlock are thos with bottom mounted impellers. if the impeller is in the lid/top part, it could airlock. this is usually only a major concern if hte CO2 tank is almost empty, adn does a tank dump forcing tons of co2 into the filter.

 

[tazcrash69]

If there are no bubbles coming out that means that the gas is being absorbed by the water, which is exactly what you want. I have a fluval 304, and it used to pull in small air bubbles (pre-planted airstone), and you didn't hear it in the filter. After a while though you want to make sure that the gas isn't building up in the top (as Malkore points out), and that you end up running dry.