# CO2 injection through filter?



## Manrock

I inject my CO2 directly into my filter intake. This smashes the bubbles up and then they are spread around the tank via the outflow pipe (and flow pump). I do this because I believe that it's a more efficient (read 'cheaper') way to get the CO2 to my plants (happy to be corrected). I used to be able to actually see the bubbles move around the tank. Now I can't. I assume the CO2 is being completely dissolved into the water column while in the external filter cannister. Drop-checker still green. Any thoughts/musings would be appreciated.

Steve


----------



## Dolly Sprint 16v

Steve

Injected co2 via filter for years with no problems. People do say that it damages the filter seal -  i have not come across this

Paul


----------



## Easternlethal

I wouldn't worry either. Any efficiencies gained from reactors vs diffusers vs filters etc. are tiny compared to loss due to surface agitation, inefficient flow and poor plant mix. Professionals can get just as good results from a sample diffuser.


----------



## Manrock

Cheers Paul and Eastern - I have also been doing this for years but I was wondering about the lack of visible bubbles now. Is it better to have all the CO2 dissolved or in micro bubble form? I've read different things about how the plants uptake CO2 - most saying it has to be in bubble form rather than completly dissolved?


----------



## AverageWhiteBloke

That's a question that's been doing the rounds for many years and I don't think you will get a one size fits all answer. Everyone has a different opinion on it. One school of thought is that tiny bubbles that stick to the leaves are better because co2 is on the surface of the plants and they can draw their carbon from it. On bigger tanks people tend to use reactors which totally dissolves the co2 because they can put more in and gas isn't wasted by reaching the surface before it's dissolved essentially doing nothing except dissolving some of it on its short journey up and out. Some people just don't like to see bubbles in their tanks.


----------



## Manrock

I'll keep it going through the filter then I think.

Cheers


----------



## AverageWhiteBloke

Came across this from @George Farmer from this post.



> Most inline diffusers are designed to be place on the outlet, so the CO2 microbubbles or mist can be distributed effectively throughout the water column. CO2 like this, in its gas form, is more efficient at delivering CO2 to the plants. It also means that one can run a comparatively lower dissolved CO2 level in the aquarium, yet still obtain enough CO2 for the plants.
> 
> However, this method does require excellent water circulation in the aquarium to enable the CO2 mist to reach _all_ parts of the tank and plants. In poor circulated tanks some plants will be getting plenty of CO2, others will starve and algae will proliferate.
> 
> I have noticed that in tanks with lower levels of circulation it's better to have the CO2 100% dissolved. It seems that the CO2 is more easily distributed this way, and all the plants stand a better chance of getting their required CO2.
> 
> This assumption is based on experience with various set-ups and differing CO2 delivery methods, from ladder diffusers, to ceramic discs placed at the opposite end to the filter, to inline diffusers place on the inlet and outlet.
> 
> For me the hobby is more about aesthetics than pure plant growth and gardening. So I have an inline diffuser placed on the inlet. This means I don't get millions of white bubbles all over, spoiling the aquascape. The trade-off of this vs. risk of the filter leaking (I haven't had an issue in over 7 years of CO2 being pumped directly into filters in one way or another) and better plant growth is worth it, in my experience.
> 
> So, in summary; if you want the best possible plant growth and have excellent water circulation, and don't mind seeing lots of bubbles floating about, then positioning your inline diffuser on the outlet is the better option.
> 
> If you want 100% CO2 diffusion and no bubbles then the inlet is an option.



Explains the situation far better than I could.   I'm thinking of returning to an inline diffuser but can't really make my mind up.

*The pros*
On inlet for me is better co2 dissolution and no bubbles in the tank, it only left after co2 was knocked off a couple of hours of viewing time where I could see the tank in its full glory and crystal clear water.
*The cons*
I'm guessing like others have mentioned on the inlet the ceramic is going to get dirtier quicker which requires more cleaning. On the inlet that means either completely removing the inlet pipe or draining the tank down too far so I can remove the diffuser for cleaning whereas on the outlet I can just drain down enough water to lower than the lily pipe to empty water out of the pipe or, put some sort of connector just before it on the inlet like a Eheim double tap so I can knock off the inflow without draining down but that's more plumbing and more faff and I don't do faff.

Decisions, decisions


----------



## Daveslaney

Try this


Makes the plants do this,With no co2 mist in the tank.


----------



## Progen

Errrr ... Now I'm definitely a newbie but I think that if you have your CO2 output being sucked into the inlet of your external canister filter, the main reason why you're not seeing bubbles could be because they're trapped on top all around the out tube and even impeller chamber.

The reason why I think that is because every now and then, air gets sucked into my canister from the skimmer but none's coming out which means it's trapped inside the canister filter unless you have something like a Fluval FX6 with an auto purge function.

I'm sure most of the gas will eventually make its way into the water but it's worth bearing in mind that during the first hour or so, what goes in is not what comes out.


----------



## Daveslaney

Thats the reason i use the filter booster run in reverse flow. Water in atop out at bottim filled with plastic pan scourers between the filter outlet and the return to the tank as a reactor if you like. Completely dissolves the co2 and no mist in tank.
When i tryed the diffuser in the filter inlet what you said was happening and every so often the filter would burp a load of co2 out in one go.
With there being no impeller in the filter booster and the water is just pushed through by the flow from the filter this doesnt happen.


----------



## Zeus.

Progen said:


> Fluval FX6 with an auto purge function.



Works a treat on mine, the FX6 stops for few mins every 12 hours so you just need to make sure you switch it off for moment an hour before any CO2 injection. Plan to have it do it on a schedule on my PLC. 
Yes the water runs pretty clear/micro bubble free. except when the other CO2 line is on the independent line, then its like Christmas for 30 to 40mins. then its off for rest of day, use it to rise the [CO2] quickly on High bubble rate.


----------



## Progen

Daveslaney said:


> Thats the reason i use the filter booster run in reverse flow. Water in atop out at bottim filled with plastic pan scourers between the filter outlet and the return to the tank as a reactor if you like. Completely dissolves the co2 and no mist in tank.


 
You could have saved yourself some money by making this simple modification to your Sunsun prefilter.





However, I use that valve for purging after filter cleaning nowadays and route the CO2 from the T-connector instead so it wasn't a wasted modification.


----------



## ChrisP

I went this method for years without issue.


----------



## Daveslaney

Think it depends on the brand of filter. Apparently the burping doesn't happen with Ehiem filters and some others. But it happened when i tryed it on my Tetratec 1200 maybe its the impeller design?


----------



## Progen

I think it's less likely or self rectifying if the top of the chamber slopes towards the impeller because gas will roll towards it and be pushed down again by the water flow.


----------



## Aeropars

Daveslaney said:


> Think it depends on the brand of filter. Apparently the burping doesn't happen with Ehiem filters and some others. But it happened when i tryed it on my Tetratec 1200 maybe its the impeller design?



I have an Eheim Pro e3 which is rated at 1850 LPH. When I put a bazooker atomiser under the filter inlet it most certainly caused burping. I have since moved to an in-line diffuser on the filter outlet. I don't mind too much the bubbles but may give it a try on the inlet and see if there are any burping using this device.


----------



## Manrock

I have an Eheim and have never had any burping issues.I have used this method for 5 years plus, just wondered if it was as efficient as I thought it was or if there is a better (cheaper) way to deliver CO2. I guess not.

Cheers


----------



## foxfish

The main issue I see with this method is the fact you can not see what is going on inside the filter.
It is quite obvious that this method works for lots of people but I wonder how much gas might build up inside the filter by the end of the day?
In some cases I would think quite a lot, this may or may not be an issue. Burping is an obvious sign of gas build up but it could be that the build up is not burped away but the built up gas continues to be release long after the solenoid is switched off.
 Again this might not be an issue but it would be a waist of gas!
There are lots of negative post about the method although there are probably more positive post so it would seem there are lots of variables that play a part in this methods efficacy.


----------

