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Sponge filter mod to allow inline CO2 dispersal

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In my two Dennerle 10g’s I have always used GLA atomic diffusers as well as Dennerle Eckfilters.

These are both shrimp tanks containing BKK, Blue Bolts, & various neocaridinas, which is irrelevant...



I find that cleaning the Dennerle Eckfilters can be quite a pain in the butt, also it’s lack of biofiltration after cleanings.



I use sponge filters in my other shrimp tanks but because these two tanks run CO2 I have chosen not to have an air pump running all day (only when the lights are off).



I have made a few changes to a sponge filter thinking that maybe I can figure out a way around this problem.



I’ve attached a small submersible pump to the top of the sponge filter to avoid using the air pump. Where the air tubing would normally attach I was thinking about hooking my CO2 line.


I am very hopeful that this might help CO2 dissolve better into the water column after running through the submersible pump.


Does anyone know if I will be able to get away with this setup without having to use any type of diffuser INSIDE of the sponge filters tubing, or if this will be safe to run?


I have considered that I possibly might need to make some type of spray bar and have the CO2 line come in at the base of the bar where it meets the pump so that I do not have air bubbles running through the pump if it turns out that it could be damaging it.



CDA Enterprises



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  • 1 month later...

There are lots of diffuser designs out there that use a powerhead to chop up the co2 bubbles and disperse them.  If you don't mind the soda pop look to your tank you will be fine.  All co2 does is make plastic brittle overtime so keep that in mind.  If you do notice it causing problems you can always add a Venturi to the pump output and run the co2 after the impeller.

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I would suggest using a small overturned plastic bottle suctioned to the glass to dose CO2. Its a pretty shrimp safe way of ensuring that you don't gas your shrimp since the CO2 content would only go down when the lights are on (as the plants are using it). You could also visually inspect the level of Co2 in the bottle and top up when necessary :) Only downside is that aesthetically its not really pleasing though personally I like my tanks with hints of DIY equipment in them :P 

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Hi there,


I would like to share my experience in DIY CO2. The best and most efficient way of diffusing CO2 is by using a water filter housing (e.g. https://www.filtersfast.com/Pentek-158116-Filter-Housing.asp) and a piece of PVC pipe, which goes inside the housing. This diffuser only works if you have flowing water in-and-out of your aquarium (obviously, you need a pump) and a pressurized CO2 source. The idea behind the design is that constant water flow increase CO2 contact. Imagine you have an infinite surface area between CO2 and water (I'm not going to talk about gas-liquid equilibrium and mass transfer for convenience). The water flows really fast while CO2 gas injects really slow. You won't see any bubbles coming out of the housing, which means perfect diffusion of CO2 in water. If you do, you might have a very fast CO2 flow.


Word of advice: CO2 is more soluble (I believe 20x) in water the oxygen. Also, CO2 solubility increases as water temperature decreases. So be careful on running CO2 under cooler temps.

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