CO2 through filter?

[Cor]

A small but tricky question:
if you allow high levels of CO2 (target 30ppm) to dissolve through the filter, nitrification of the bacterial culture can seriously reduce because the pH drops too far?

thoughts, comments

Thanks in advance,
Cor

 

[oscarlloydjohn]

Yes, I suppose the CO2 could reduce the efficiency of the nitrifying bacteria as the optimum pH is higher than 7.0

If the efficiency of the bacteria is lessened, more bacteria will grow to compensate until all/the majority of ammonia and nitrite are being oxidised.

Not sure if any of that is correct but that's my perspective on it.

 

[Zeus.]

But if you don't use the filter as a CO2 reactor and your tank pH is less than 7pH so is the pH in the filter so will have the same effect IMO. Obviously if the filter is doubling up as a CO2 reactor the localised pH drop in the filter will be slightly more than in the tank but not much IMO

 

[john10001]

Isn't it likely to damage the impeller doing this?

 

[Matt @ ScapeEasy]

I've heard that is can damage the rubber seals too... not sure if there is any truth in this though?

 

[zozo]

In the very beginning of my carbon days i noticed a perfect fit to attach the glass in tank pollen difusser to the glas filter inlet. So all the co² bubbles rose up against the inlet and all got sucked in.

The only issue i noticed after a while was the pump burbing and slurping a lot from the acumulating non dissolved co2 in the top of the filter.. It became worse over time the filter got more dirty.. I tried to imagine what happened in the filter and guess it also accumulated co2 bubbles between the sponges and the inner filter canister wall and in between the spaces of teh biomedia, than release and accumulate again in the filter top. Making the impeller run in a bubble of co2. Since these pumps are non self priming it results in strange noises and sometimes minutes no flow. Shaking the filter also resulted in trapped bubbles releasing and burbing of the pump.

Thus in my case theoreticaly it was a good idea, practicaly on the long run it didn't work that well as expected it didn't realy correspond with a monthly filter clean. It needed a lot more attention. So and i switched to an inline diffuser in the filter outlet to resolve that issue.

I guess that's the most likely issue you could run into first.. It probably depends on canister size, flow through, filter media etc. etc. in how far this issue can play up.

 

[Edvet]

Depending on tank size i would always advise a (DIY) reactor on a separate pump if possible.

 

[ian_m]

I've heard that is can damage the rubber seals too... not sure if there is any truth in this though?

Yes CO2 does dissolve in rubber, which is why Teflon washers, as opposed to rubber washers are used on CO2 cylinder outlets. I once used an "air line" one way valve in my CO2 line and after a while the rubber flaps in the valve just melted.

 

[dw1305]

Hi all,

if you allow high levels of CO2 (target 30ppm) to dissolve through the filter, nitrification of the bacterial culture can seriously reduce because the pH drops too far?

No, you will just get a slightly different assemblage of nitrifying organisms than the one that you would have had without the CO2, but you won't lose significant nitrification potential. Have a look at <"Will filter bacteria.......">.

There is are some up-dated scientific references since 2016, probably the most relevant is <"Freshwater Recirculating Aquaculture System Operations Drive Biofilter Bacterial Community Shifts around a Stable Nitrifying Consortium of Ammonia-Oxidizing Archaea and Comammox Nitrospira">, I think that it should be "Open Access".

Micro-organisms
Nitrifying organisms use <"DIC as their carbon source">, so adding CO2 may actually improve nitrification rates, when you add CO2 you have higher DIC levels then you would without it. In non-planted tanks nitrification is often limited by oxygen availability.

Plants
Additionally when you add CO2 you have enhanced plant growth, which produces more oxygen and also a larger rhizosphere in the substrate, both of which enhance nitrification.

A simple way of thinking about biological filtration is that when plant growth is enhanced then biological filtration capacity is likely to be enhanced as well.

cheers Darrel

 

[foxfish]

It is a popular method, mainly used as there are few affordable alternatives that produce a mist free tank.
The method is not ideal but it most certainly works for many people, a build up of C02 inside the filter resulting in several large bubbles escaping is the most common complaint. (Burping)
Personally I am not a fan simply because I can not see what is happening inside the filter, if there is a build up of gas, or how long it take to get rid of any build up.... but it is a viable option for some folk.

 

[Zeus.]

pump burbing and slurping a lot from the acumulating non dissolved co2 in the top of the filter..

Had this on my FX6, couldnt get the BPS high enough to hold a steady pH without it spitting CO2 out, then I went for x2 APS EF2 reactors post filter

 

[Marc Davis]

My canister is 1000l/h and a decent size. I also had the same issues of undissolved gas sitting in the filter and causing it to be noisy and not working properly.

Of course, you can just give the filter a knock and a tilt, but then you get a load of crap pumped into the tank.

 

[orinoko]

Hi. I have one question. Isn't there a problem with the humidity in the room?