what determines the capacity of a diffuser?


12 Nov 2009
I've been looking at various diffuser in ebay. Some have 2in diameter (which I assume is the ceramic disc) and is rated at 40 US gallons. while some with 1in diameter is go up to 75US gallons. So what determines the capacity of a diffuser?

I've searched the net and forums but came away empty. thank you :)


29 Jan 2008
When looking for a ceramic diffuser, you mainly need to be concerned with the amount of co2 you are going to be passing through the disc. Therefore, it's mainly about the pressure within the glass rather than the ceramic disc itself. Too much pressure and the glass will break.

I guess it also depends if you want something that is machine made (cheaper) rather than hand made from the liks of Do!Aqua and ADA.

You didn't indicate what size of tank you are looking to get for the diffuser.

If I was you, I'd get the biggest disc size possible that wouldn't look out of place in the tank.


25 Oct 2008
Budapest, Hungary
larger ceramic also helps to extend the maintenance period.
if you have a smaller one you would use the full capacity (or more) or the ceramic, so any algae on the plate would decrease the efficiency quickly. at the end you need to clean very frequently like weekly or often and still not get the right efficiency out from the ceramic.

CAL is also handmade glass it's just not that clear like the ADA one.

A cheap diffuser mostly work the same as a quality one. And you can have another one for replacement if you broke or clean it.

Quality diffuser ceramics produces better mist, and the algae not cover the ceramic too quickly.

Mark Evans

13 Jun 2008
newark notts.
Superman said:
Too much pressure and the glass will break.
i dont think that will happen. That's what regs are for.

ever tried putting an empty co2 hose into tank water without a diffuser?....you'll see that the reg has done it's bit buy reducing pressure to a manageable rate. even on full whack you'll never break the glass....unless every single whole is blocked.

Graeme Edwards

21 Jun 2007
Wirral/Chester Cheshire.
The way I see it is this :

Lets work with a 35L tank say, nothing to big. If you put around 1-3 bps of Co2 in to that tank, that would normally be the right amount - thats what you would be aiming for right!

So you compare pumping 3 bps through a Rhinox5000 ( approx 4cm diameter ) as a pose to a nano diffuser by Dazs ( approx 1 cm in diameter ) To my experience you would find a healthy fine mist of bubble lifting off the nano diffuser at that bubble rate, yet with a Rhinox you would find a small section producing bubbles, and IMO much larger than with the nano. The larger bubbles have less surface area and rise to the surface much quicker.

Also, think about it like this.
To much pressure on a nano diffuser. eg 5-6 bps could force the Co2 line to constantly pop off. On the other hand, to little passing though a large diffuser eg 1 bps would result in a week delivery of Co2 and it would no doubt find the weakest point of the ceramic plate and do as described above....( finding the path of least resistance ) = large bubbles rising to the surface to quick. The right size diffuser gets away from this problem as all of the diffuser is used, thus more efficient.

You do also need to take into consideration the quality of the ceramic plate. Even if you get the right size given its pressure requirements, there still could be flaws which would result in rapid bubble loss rising to the surface,

That my slant on it any way, and it works for me.


17 Apr 2008
The BIG End, South Wales
I remember George saying he spent a lot of money on an ADA diffuser for it to not be as good as a cheap version he had. Much of it is down to pot luck with how good the quality of the ceramic disc is. I've noticed this with my two cheap Spiro diffusers - 1 releases many ting bubbles across the whole surface of the disc, the other releases large bubbles on only half of the disc.