could I use co2 with a sponge filter or should I get a hob?

[Jacob Hill-Legion Aquatics]

I was wondering if I could use co2 with a sponge filter? would it get diffused evenly and well? what would be the best placement? should I just get a hob? I also have an extra wave maker I could use to disperse the co2.

 

Edited October 19, 2022 by Jacob Hill-Legion Aquatics

[AllFishNoBrakes]

I have C02 on 4 of my tanks. They all have a sponge in the back left, and a HOB in the top right. Diffusers are placed on the right side by the HOB. You can watch the bubbles rise up, and then get pushed back down and around thanks to the HOB. 

Works for me, but I’m also not shooting for maximum C02. Just enough so my plants don’t run out. 

[nabokovfan87]

you definitely, absolutely want to have a diffuser for CO2 and not use something like the sponge (or HOB) to feed in the CO2.  If you use a HoB in the method that Cory has shown, the key there is that the CO2 feeds into the intake of the HOB and then the impeller breaks the bubble into micro bubbles.  The flow pushes the bubble around the tank, and then that diffuses into the water. 

What you're looking for is to get the bubbles as fine as you can, diffusers are cheap and extremely easy to care for.  They seem intimidating, but it is literally the most visual part of having pressurized CO2 and what is attributed to the "beauty" when it turns on for you each day.  I find myself enjoying watching the bubbles come out, especially when it's doing it's thing and the tank is doing well. 

You likely don't want to have the CO2 next to the sponge, but you probably want to have a pumphead or some sort of spraybar type of output to push the flow across / around the tank pointed towards the diffuser in some capacity.

The sponge will simply push the bubbles up and they likely won't go back down / around the tank easily.   Especially without being diffused beforehand.

[Jacob Hill-Legion Aquatics]

@nabokovfan87yeah I would be using a diffuser  but I was just wondering if I should use a wave maker I have to diffuse it. so this helped, I really just want enough co2 for the plants to not run out because im just growing java fern and anubias. and Ive really noticed a difference in the plant health when I have co2 on the tank vs not. and I already have a co2 system, also Im trying to save as much as I can with this tank that's why I wanted to do a sponge filter.

[nabokovfan87]

On 10/19/2022 at 5:03 PM, Jacob Hill-Legion Aquatics said:

@nabokovfan87yeah I would be using a diffuser  but I was just wondering if I should use a wave maker I have to diffuse it. so this helped, I really just want enough co2 for the plants to not run out because im just growing java fern and anubias. and Ive really noticed a difference in the plant health when I have co2 on the tank vs not. and I already have a co2 system, also Im trying to save as much as I can with this tank that's why I wanted to do a sponge filter.

As far as CO2 goes... the "best" method is going to be a spraybar for circulation.  I think, but have never seen someone mod a sponge filter to make that happen.  The ACO sponges with a ziss stone would work a bit better in terms of circulation because the bubbles are finer compared to some of the other designs and you can control the size.  Regardless of CO2, that's just where my thought process goes to get atmospheric CO2 into the tank as well as other means, directly with pressurized CO2.

With anubias, java ferns, I think you'll be better off with a hang on back, literally anything to push flow around.  I opted for a Sicce Nano pump that I modded with a spraybar and it wasn't straightforward, but I think it'll be a constant on all my tanks moving forward ~20G or smaller.  I really like the use of that type of an output much moreso than any others (hob, etc.) compared to previous methods I have used. 

That being said.... the "easiest" or cheapest is going to be using a hang on back on the side of a tank as opposed to the back.  This forces the water across the top of the tank, then down into the diffuser (hang on back on one side, diffuser on the opposite side).  It isn't an option for every tank, but that's worked very well for me previously to get good circulation.  Very dependent on tank geometry of course.

EDIT:  Clearly, the "best method" is a canister with in-line diffuser.... potentially, but a good spraybar setup is still beneficial in that situation for dispersing the co2 across the tank.

[B7gwap]

There is a cool video @Cory did where he visited a LFS in San Francisco that used upside down Gatorade bottles lashed into the back corner with suction cups and a little float indicator nug of polystyrene foam, and the owner had tons of just awesome overgrown jungle tanks. Rather than use a regulator in every tank or even shared, he would just go fill the upside down bottle with gas until the float was almost at the bottom using one tank and a gooseneck spray bar with a trigger release. 
 

Ive done some experiments with upside down Tupperware floating up against the canopy, the idea being that gas dissolves into a liquid as a function of its surface area. It why more, finer bubbles works, and why you want them to stay under water for as long as possible.
 

The method in the video makes a very large interface of gas to water that stays in contact until all the gas is dissolved or is topped up.