Inline diffuser working pressure/BPS questions

aquascape1987

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Hi all. Sorry if this is longwinded, but here goes....I’m currently running a CO2 Art Pro elite series dual stage regulator with a new CO2 Art in-line diffuser on the return to tank side of the filter, and have been struggling to get the CO2 set correctly to get a lime green drop checker for lights on, after 2 hours of injection before lights on.

I’ve been questioning the efficiency of my co2 dissolution for a while now, due to having to have a ridiculous bps injection rate to get the drop checker anywhere near Lime green, even after 4 hours of pre lights injection. I’ve also had 2 long term diatom explosions that I feel are probably related to this problem, as well as flow distribution due to my hard scape, (currently have a power head on order to resolve any dead spots).

I have had the diffuser 7 months, and have always had quite large bubbles getting through to the tank, rather than a fine mist, which I suspected was likely the issue. I’ve been baffled by all of the reviews on here claiming the fine mist out put of the device .But today I realised that at some point a long time ago, or even from the word go, I reassembled the diffuser incorrectly after cleaning/ in the first place and actually have had one of the rubber Seals in the wrong place since then. I had 2 rubber seals together on one side of the ceramic tube and no seal on the other side, and I’m guessing that the co2 was getting into the flow in large bubbles either between the two seals or on the other side where there wasn’t one because after putting back together correctly, I finally have a fine mist output that everyone else has been getting. I have to say though, when I realised it was like a real slap your hand across your forehead ‘Eureka’ moment. The sort where the joy you feel is almost negated by the feeling daft for taking this long to work it out.

In the months of frustration and reading I’ve done to try and solve this issue, I first suspected it may have been a working pressure issue, in that I was running the working pressure valve always fully open on my regulator, therefore always operating at maximum working pressure. My thought process on this was that perhaps the pressure was too much for the diffuser and was forcing co2 around rather than through the ceramic tube and therefore causing the large bubbles and ineffective co2 dissolution. Consequently, I reduced the working pressure to 30 psi from fully open (45 to 50 psi) Although this turned out not to be the issue, it has got me wondering now that I am finally on a better track to set up correctly....

1) Does the working pressure used affect the performance of the diffuser in any way in terms of the fine mist it produces. Eg is there a difference in performance between using higher and lower working pressures using the same BpS count for both different working pressures? You can achieve the same BpS through the bubble counter by altering the working pressure dial, or altering the needle valve, but is an injection rate of say 2 bubbles per second the same at either 30 psi working pressure, as it is at 2 bubbles per second using 50 psi working pressure?

2) Depending on the answer to the above, and if the working pressure used is important beyond the minimum pressure that the diffuser needs to work correctly, what working pressure should I be setting?
 

Zeus.

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BPS is only a rough guide of injection rate. If you increase the working pressure the BPS will increase and/or the bubble size and bubble internal pressure.
I control my injection rate by increasing/decreasing the working pressure.

I have big bubbles but use DIY CO2 reactors so nothing lost just trapped in reactor
 

Kalum

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Not quite, being really pedantic it might affect bubble size due to varying pressure (hence why bps should only ever be a guide) but what you'll find is is you leave the needle valve set at 2bps at 30psi then it will more than likely increase to say 3bps at 40psi

What sammy mentioned above does partly answer your first question, most diffusers have a minimum or optimal working pressure for them to operate correctly (or at all)

You should refer to the instructions from the manufacturer for the specific diffuser you're using, for reference I use the same as you and have it at 40psi
 

aquascape1987

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Thanks for your response Kalum. I suppose I felt Sammys response was merely stating the obvious that every diffuser has a minimum pressure input required in order to operate, something I had already stated myself in my opening post.

I’m aware of the fact that BPS is only a guide or a form of visual yardstick to use to gauge how much CO2 you are injecting but that’s not really the info I’m picking at.

I’m NOT looking for someone to tell me how many bubbles per second will get me a 1 pH drop or so many PPM of dissolved CO2 in the water column. I’m looking to understand the mechanics of how (if it does) the working pressure setting effects the efficiency of getting the CO2 into the water through the diffuser.With an understanding of that and at that point, I can set the working pressure accordingly and then work out by trial, error and tweaking, the correct injection rate from there using a combination of the drop checker, PH profile, observing my fish tolerance to the increasing CO2 being added (to allow me to push the boundary)as well as plant health.

So in hindsight I might not have been as clear as to what specific useable information I was looking for, which is....Whether or not there is any benefit in running the working pressure higher than the minimum required by the diffuser. Will the diffuser create a finer mist with a higher working pressure, therefore making the dissolution of that mist more readily dissolvable in the water. Or does increasing the working pressure beyond the minimum required by the diffuser. carry no benefit/ efficiency at all?
 
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aquascape1987

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Hi Zeus the tank is approx 85 litres. Filter is Eheim professional 4 250T. Water temp is 23 degrees C. I’m ok with how to fine tune the amount of CO2 input, just looking for advice/understanding the working pressure setting before I start with the re tweaking to get the dissolved CO2 correct
 
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jolt100

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Hi all, I haven't done any proper experiment to corroborate the following but base my suggestion on work I used to do.

The ceramic diffusers have small interconnecting passages like bubbles in a piece of foam. All the bubbles are not the same size but all are sub micron and the surface pores could be the full diameter of the bubble or just a small section cut off the edge. On the inside, active, surface of the diffuser with no flow, the pressure from the regulator has to overcome resistance of the easiest route through the diffuser and this will occur at one of the largest pores. A bubble will start to form and the size and rate of growth of the bubble depends on the pressure, and the availability of surface active substances in the water( lipids, fats etc) which coat the bubble surface and stabilise it, as well as the solubility of CO2 in water. As the pressure increases the rate of bubble formation increases but the smaller pores also start to produce bubbles with a smaller diameter which may be more stable.
In a dynamic environment where water is flowing past the surface the bubbles will not be able to expand as much and will be torn from the surface at a smaller size.
I would suggest that it's trial and error to optimise each set-up and as long as the minimum pressure is exceeded you will have a range of bubble sizes but if the pressure is higher there will be more large bubbles.
The mechanics of bubble formation and stability is quite complex and I apologise if my explanation is a bit garbled.
Cheers
John
 

Wookii

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Hi Zeus the tank is approx 85 litres. Filter is Eheim professional 4 250T. Water temp is 23 degrees C. I’m ok with how to fine tune the amount of CO2 input, just looking for advice/understanding the working pressure setting before I start with the re tweaking to get the dissolved CO2 correct

To answer your main question, I have the same regulator as you, but the JBL inline diffuser. I always set my working pressure at 2 bar, which is a sniff under 30 PSi, I've not had any problems so far. My previous Aquamedic regulator had a fixed operating output at 2 bar also.

I also have a DIY reactor after the diffuser to help dissolve more of the bubbles before they are released into the tank. I still get some small fine bubbles, but not as many as I would without the reactor.

As another data point, in case it is useful, my tank is a little smaller than yours at 60 litres, but it still takes around three hours to get a 0.8 Ph drop. I have tried to go for the full 1.0 Ph drop, but my Amanos go a little crazy doing laps of the tank when I've done that, telling me I'm pushing the CO2 a little too far. I get a nice light green drop checker at 0.8 Ph too. On my tank, that's approximately 100 bubbles per minute (1.67 bps).
 

aquascape1987

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Thanks for replies guys. I think these help me out. I’m going to keep the pressure at about 30psi and use the needle valve from there to tweak. Current setting has a lime green drop checker at lights on but I fear it’s a bit high as it’s yellow by the time lights go off. Tank is also like 7up, so I’m thinking of switching it to the other side of the filter circuit. I know some say it can damage filter seals, but I have done this successfully long term in the past. Hopefully the finer bubbles I’m getting through the diffuser now will help with full dissolution in the filter without large burps. Any thoughts on this from anyone?
 

Wookii

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Thanks for replies guys. I think these help me out. I’m going to keep the pressure at about 30psi and use the needle valve from there to tweak. Current setting has a lime green drop checker at lights on but I fear it’s a bit high as it’s yellow by the time lights go off. Tank is also like 7up, so I’m thinking of switching it to the other side of the filter circuit. I know some say it can damage filter seals, but I have done this successfully long term in the past. Hopefully the finer bubbles I’m getting through the diffuser now will help with full dissolution in the filter without large burps. Any thoughts on this from anyone?

It's entirely up to you of course, but if you put the diffuser on the inlet side, the detritus from your tank will coat the inside of the diffuser's ceramic tube in a matter of days I would imagine, resulting it is dispensing larger bubbles.

You would be better off adding a reactor after your diffuser if you want to achieve better dissolution of the CO2 and less bubbles in your tank. These are relatively simple to DIY, or you can buy one off the shelf.
 

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