Aquarium Commercial In-tank CO2 Reactor Review

One of the ways to inject CO2 into the aquarium is by using a reactor. Reactors are great way to inject CO2 because it promises high dissolving rate and almost no bubbles so your aquarium will not look like a soda. But the greatest advantage, from the point of DIY CO2 users, is you do not need to have high pressure in order to use a CO2 reactor. And you can also make your CO2 last much longer than using a diffuser.

However, CO2 reactors also have their down side. For one you will need to add additional powerheads in your aquarium and that is yet another piece of item in your tank besides your heater, surface skimmer, and what have you.

Dymax CO2 Diffuser MD-103

I bought this for my 75 gallon at first but found it too small for such a big tank. I later used it on my 20 gallon.

Dissolving Methods:

This is a simple reactor design whereby water flow will generate a vortex at the top of the reaction cylinder and CO2 comes into contact with high water flow and gets dissolved into the water. There are three spinning balls which are supposed to aid in further CO2 dissolving.


I had a 800L/h water pump connected to the reactor using 1.5 big bubbles per second CO2 flow rate.


The reactor worked fine on the first day. Only two out of the three balls were spinning. The bottom ball became a hindrance to flow actually. CO2 level was in fact lesser than when using a atomizer diffuser.

I increased the CO2 flow rate to about 2 bubbles per second by the additional CO2 was not getting dissolved. The CO2 air pocket above the the reaction cylinder began building up and eventually escaped as undissolved big bubbles.

So with a 800L/h water pump the maximum CO2 injection was just 1.5 bubbles per second. IT wouldn’t  accept anymore. I was contemplating on using a higher flow water pump but that will make my tank into a washing machine.

On the third day, only the top most ball was spinning. And finally at the end of the third day all three balls stopped spinning.

After a quick clean I managed to get all three balls spinning again, but only to find the same problem after two days again.


This is one of the most affordable CO2 reactor in the market. If you have a small tank this will work just fine, if you don’t mind the constant cleaning.

Dymax CO2 Diffuser MD-107

I bought this after purchasing the MD-103 for my 75 gallon tank. The MD-103 was insufficient for such a big tank so I thought a longer MD-107 would do the job.

However, I was wrong. The MD-107 was a complete rubbish! The cylinder housing and the rolling balls are too tight. As a result the balls cannot spin at all!

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I was unable to get this to work because of an apparent design flaw.


Do not buy! It should be removed from the shelf in the first place!

ISTA External Turbo Co2 Reactor Diffuser

Well, I must say this reactor looks kind of similar to the Sera one. I did not have good experience with this reactor.

Dissolving Methods:

The intake is from the side together with the CO2. Water and CO2 upon entering the housing will be met with two blades. The velocity of the water entering will propel the blades.

The revolving blades will stir the water and cause CO2 to be dissolved into the water. Water then escaped by entering from the bottom of the center tube. CO2 will be kept floating at the top unless they are dissolved into the water.

First, it takes 12/16 inch tubing, and none of my existing Fluval canister filters uses 12/16. The only filter I have that uses 12/16 tubing is a Shiruba filter.


Next problem, my Shiruba filter did not have enough flow rate to power this reactor. So I gathered all my tube reducer and used a 800L/hr water pump to push it. But it is quite futile. The water upon entering the reactor slowed to a trickle. No dice.

Then I used a 1000L/hr powerhead and managed to turn the blades in the reactor. Nice. But somehow the air pocket within the reactor cannot escape. After an hour the air pocket was still there. And I am beginning to lose my patience. Time to refer to the user manual, but the only problem is, there’s none!

On an obscure corner on the box, there is a line that stated that I will need to invert the reactor to eliminate the air pocket.

With all those tubing, inverting the reactor is next to impossible! After a lot of trouble I managed to get rid of the air pocket.

Disaster struck the next day. I found myself staring at a fish tank 3/4 filled with water. The reactor has developed a leak overnight. I did not isolate the leak but after dismantling and reassembling the reactor the leak was no longer there.

As one problem get solved another surfaced. Just after two days some debris got into the reactor and the blades were not spinning as fast as they used to.


I never get it to work in the end, but if you do, please let me know how it performed. Too much hassles in my opinion.

ISTA Max Mix CO2 Reactor

This is one of the better reactor around. The price was really cheap and it dissolved CO2 well.

Dissolving Methods:

Water enters from the top at the side and turns two blades. CO2 is enters from the top and stay on the top.

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As the blades turn CO2 gets dissolved into the water which then escape by enter the center shaft tube from the bottom.


I use a 900L/hr power head to power this reactor. The reactor comes with a L tube which you should affix to the top to deflect the outflow.


There was not much visible bubbles. Blades ran well with a 900L/hr power head. Occasionally you will need to do simple flushing to get rid of debris.

The downside of this reactor, the intake is from the side and outflow is on the top. WTF? You will need to fit the 90 degree pipe to deflect the flow. Also the suction cup position is awkward. It forced you to run the reactor in certain direction only. The reactor is also VERY BIG. On my 75 gallon it look like a sore thumb. I could not hide it in the background because of the suction cups’ position.

But the main problem that I faced was the fact that it cannot dissolve enough CO2 for my 75 gallon tank. When I turned up the CO2, the reactor kind of reached a threshold for dissolving, and the gas just accumulated until it get ejected into the water as giant bubble. Changing to a higher flow rate power head resulted in the tuning getting lose because the piping diameter is really small. Relocating to a smaller tank was not possible as the flow rate to power this reactor will make your tank like a washing machine, and the size of this thing makes smaller tank implementation undesirable.


A poor-man reactor, can be cheaper than DIY reactor. However, big foot print and mismatched flow rate makes this reactor undesirable for neither large tank nor smaller tank.

Huey Hung Aquarium CO2 Power Atomizer

This is an accidental find actually. I was looking for a high pressure DIY CO2 canister on Taobao when one of the recommended searches displayed this reactor.

I now have these reactors in ALL my tanks!

Dissolving Methods:

Strictly speaking, it is being marketed as an atomizer rather than a reactor. But the way I see it, it is some sort of a hybrid Cerges reactor cum atomizer. It creates both CO2 saturated water as well as micro bubbles.

It has its own impeller that spin water rather than depends on an existing flow from your filter or powerhead.

The actual working of this reactor is still unclear though. The main reactor housing consists of an atomizing cup, an intermediate chamber, and an inner chamber! 3 chambers in total!

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Water is being sucked into the inner chamber via an opening at the bottom. CO2 is then mixed and forced out at high pressure into the intermediate chamber. In the intermediate chamber undissolved CO2 is further mixed with the water before being expelled out into the atomizing cup.

In the atomizing cup, new water flowing in is again mixed with exiting water which is already mixed with CO2.

This repeated mixing and expelling forced a high level of CO2 to be dissolved into the water. And due to the high pressure created within the chamber, CO2 are forced to dissolved into the water and when the water exits from the chamber, the pressure drops and CO2 return to gaseous state forming extremely fine micro bubbles. The result is a highly CO2 saturated water as well as micro bubbles.


The size of this reactor is still acceptable, and it comes in two different flow ratings. A 400 L/Hr or 600 L/Hr but the dimensions are identical.

In my 11g low profile tank I used the 400 L/Hr reactor. Running CO2 at about 1.5 bps, the CO2 are almost completely dissolved. Some CO2 escaped in the form of fine bubbles and was not visible from far.

In my 20g tank I used the 600 L/Hr reactor. Running CO2 at about 2 bps, the CO2 are completely dissolved.

In my 75g I used the 600 K/Hr reactor. Running CO2 at 4-5 bps, I get micro bubbles.

The manufacturer claims that the reactor is good up to 20 bps!

Overall this has got to be the best commercial CO2 reactor/diffuser I have ever used.

The biggest plus for me is that it is efficient and you do not need to connect to a powerhead or slow the flow by using the canister’s outflow. The footprint is small and you can easily hide it in the background. It is the most ideal for my low profile tank where additional power heads is not possible. In addition, I am running a HOB filter whereby I cannot use any inline atomizer or reactor.

One other function stated in the user manual is that if you invert the reactor and place it near the surface, it becomes a protein skimmer!!??

I believe the biggest problem for most reader is you cannot find it anywhere else online except Taobao.


Recently I came across a model that is quite similar and it is available on Amazon. It is worth check it out.