JBL CO2/PH computer

beeky

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I think I posed a very similar question, possibly in the thread that was mentioned previously. I was under the illusion that if pH changes with CO2, then keeping a stable pH meant stable CO2. I think one of the points mentioned to me was that pH changes aren't immediate across the whole tank, so a controller could end up oscillating the pH and therefore the CO2. I agree though that if you can afford it, a good use of a controller is to prevent CO2 dump from a near exhausted bottle and gassing the fish which has happened to a number of people.
 

JohnC

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beeky said:
I think I posed a very similar question, possibly in the thread that was mentioned previously. I was under the illusion that if pH changes with CO2, then keeping a stable pH meant stable CO2. I think one of the points mentioned to me was that pH changes aren't immediate across the whole tank, so a controller could end up oscillating the pH and therefore the CO2. I agree though that if you can afford it, a good use of a controller is to prevent CO2 dump from a near exhausted bottle and gassing the fish which has happened to a number of people.
With my setup would the large drop in ph I use (7.2 to 6.3) be thereby beneficial to keeping the co2 constant. I.e. the ph controller only comes on and oscillates between a range of 0.5 or approx 7% of the total initial adjustment during the day. So even with the lag or lack of direct parity between the level of CO2 and ph in the tank the actual concentration of CO2 shouldn't vary during the day much beyond 32ppm or 28ppm from a base of 30ppm? Obviously the drop checker does have a lag itself but it does show constant green.

The flip side of this in my tank is my very poor flow rate (fluval 205 doesn’t cut it) means that yes my CO2 and PH isn’t constant around the whole tank so my controller is adjusting at the wrong times anyway.

Hmm. Alot to fix me thinks.

Would the setup using the PH controller to protect from a CO2 dump work by placing a timer on the plug from the solenoid that attaches to the PH controller?

Best Regards,

John
 

GreenNeedle

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0.9ph is not a great drop CO2 wise. Mine goes from 7.4 down to 6.4 (I have no Ph controller, this is from the same cheapo test kit as I use in my DC)

I would therefore assume that if you are setting yours at 0.9 difference that you aren't getting to 30ppm anyway!!! Maybe wrong but thats my understanding.

I think what people mean when they talk about CO2 dumps is that if they set their controller to 1.1-1.2 below tank water Ph then if the bps increases from 2 to 20 when the bottle is empty the controller will stop it.

AC
 

vauxhallmark

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Just to be clear, hijac, I assume when you say the controller switches at 0.5 of a point that you mean 0.05? Or is it really 0.5?

Thanks,

Mark
 

Ed Seeley

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Bear in mind that you pH drifts around in any tank as other parameters change. Your biological filter for starters is constantly acidifying the water. As this changes your CO2 levels will change too.

To use a CO2 controller as a safety device you need to work out the bubble rate with the needle valve to give you 30ppm. You then need to have this level running with no restriction by the pH controller and measure the pH level then set your pH controller to turn the CO2 off when the pH drops say another half a degree or more. This should prevent a large amount of CO2 being released and over dosing the tank. Please note though that the bubble rate (governed by adjusting the needle valve) will then govern the quantity of CO2 in your tank and the pH controller will only kick in in some big emergency. I would also turn the CO2 off during the time the lights are off too using a simple timer on the solenoid.
 

JohnC

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Ed Seeley said:
Bear in mind that you pH drifts around in any tank as other parameters change. Your biological filter for starters is constantly acidifying the water. As this changes your CO2 levels will change too.

To use a CO2 controller as a safety device you need to work out the bubble rate with the needle valve to give you 30ppm. You then need to have this level running with no restriction by the pH controller and measure the pH level then set your pH controller to turn the CO2 off when the pH drops say another half a degree or more. This should prevent a large amount of CO2 being released and over dosing the tank. Please note though that the bubble rate (governed by adjusting the needle valve) will then govern the quantity of CO2 in your tank and the pH controller will only kick in in some big emergency. I would also turn the CO2 off during the time the lights are off too using a simple timer on the solenoid.
makes good sense, i will adopt this during my big tank revamp in a month or so.
 

Ed Seeley

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hijac said:
Ed Seeley said:
Bear in mind that you pH drifts around in any tank as other parameters change. Your biological filter for starters is constantly acidifying the water. As this changes your CO2 levels will change too.

To use a CO2 controller as a safety device you need to work out the bubble rate with the needle valve to give you 30ppm. You then need to have this level running with no restriction by the pH controller and measure the pH level then set your pH controller to turn the CO2 off when the pH drops say another half a degree or more. This should prevent a large amount of CO2 being released and over dosing the tank. Please note though that the bubble rate (governed by adjusting the needle valve) will then govern the quantity of CO2 in your tank and the pH controller will only kick in in some big emergency. I would also turn the CO2 off during the time the lights are off too using a simple timer on the solenoid.
makes good sense, i will adopt this during my big tank revamp in a month or so.
I don't think the pH controller is necessary at all though. I only use a solenoid on a timer on three tanks and I've never had a CO2 dump yet. I'd only use it if you already have it and then use a drop checker with 4dKH water in to make sure your CO2 stays at 30ppm.
 

willjones

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Hi Hoskins, I'm not massively experienced at all but I have set up a planted tank with and without a pH controller for several months each.
Using a pH controller has made no perceptible difference in my aquarium, although I can see how a pH controller could be useful in a different set up.

In my set up, I don't use a reactor, the co2 bubbles are released into the intake of my filter at a rate of about 10 per min for a 200L, fairly well planted tank. I previously used a pH controller, but this basically switched the co2 on when the lights came on, and switched the co2 off shortly after the lights went off. Once I'd worked out the bubble rate (using the co2 indicator solution), the pH controller became redundant. I think this happens because the rate of co2 diffusion in my set up is modest, so it doesn't bring down the pH that drastically. However, if you're using a co2 reactor with a higher rate of co2 diffusion, I would imagine there is a higher risk of co2 overdosing, and I would speculate that there could be more of a role for a pH controller.

Also, I know this is going to be controversial but... the much acclaimed co2 indicator, after initially setting up, I don't find that useful!
I find that it gradually changes colour over several days, even when I know the conditions in the tank are unlikely to have changed, it always starts off yellow, then after a day goes green, then blue. It's not leaking, I think the system could be flawed for a few reasons:
1. The principle relies on the fact that co2 is the only gas which can dissolve in the reageant solution - why can't other gases such as hydrogen sulphide do this? Even if present in small quantities this could change the pH of the reageant solution.
2. Molecules don't only move by vapourisation and dissolving, they can also move by brownian motion, so bascially liquids can get across to the reageant solution too. I don't know alot about this so I'm prepared to be contradicted by someone knowledgeable, but I'm just speculating that this is possible.
I would say, once you get a feel for how to run your co2 using a combination of pH monitoring and a co2 indicator, and your set up is stable, you can probably abandon both!
Thoughts?
 

GreenNeedle

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On the first point the assumption is normally made that when someone buys a Ph controller with their kit that they have gone for the works. Highlight et al. In a highligh tank where CO2 stability is much more necessary then there will be swings of a up to a point during the day.

With the drop checker I am by no means someone who acclaims the CO2 indicator. I am however one who uses two for the reason of being able to see the levels 'cheaply'.

I can't understand why yours starts at yellow and then slowly comes down through to blue. It should always start at blue with 4dKH and bromo blue. The reason we use 4dKH is because it is a known reference and after 2-3 weeks we empty rinse and refill in case of contaminants.

It should change colour over several hours rather than days. If so then something is not right with or within the DC.

I don't think anyone can say the system is flawed as it has been used for a fair few years succesfully now and was never supposed to be highly accurate, hence being called an indicator.

As for the other points I am no scientist so someone else will have to give 'real' responses to these but:

I don't see any reason why other gaseous substances can't pass through into the reagent. What works for one should work for all here I suppose. I would say though that Hydrogen Sulphide should be in such low concentrations within a tank otherwise there is a much bigger problem that you need to worry about than the drop checker. I guess small quantities could change the Ph though and therefore this point is for someone else to answer ;)

I remember something about Brownian Motion in schol and though it was something to do with heat. With the heat within the drop checker and tank water all being equalised after a short while I would've though that this wouldn't occur. Is Brownian motion the one where hot water rises and cold water sinks? If so then you have solved the nutrient distribution due to poor flow problem as we can now just heat the lower half of the tank and chill the top half and let brownian motion distribute the nutrient for us ;) Again I am no scientist and this is a question for someone else. Is brownian motion the smoke one? I can't remember science was never one of my faves.

As for the final part. Yes once someone has the feel for it they could in theory abandon both the controller and the DC but why? I never had a controller anyway and a DC costs so little to run that if working properly (changing by the hour) then it is surely a cheap safety feature that is pointless to abandon. Just for you to see here is a timeline of mine showing how quickly (at longest) they should change from fresh solution (bright blue 11am) to lime green (9pm):

photoperiodfull.jpg


Hope this helps a little.

AC
 

Ed Seeley

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Brownian motion is just the random erratic movement of molecules and particles such as dust and smoke. I don't see how it applies to drop checkers at all.

Some water (and other things in the tank water) will of course end up in the drop checker solution, but only tiny amounts and this is one reason why it's a good idea to replenish the solution every few weeks. This is evaporation and as the gaseous space inside a drop checker is an enclosed vapour lock then after a short period evaporative equilibrium will be reached and so the net evaporation should be 0 from drop checker and tank into the drop checker. This balance will be reached with other chemicals that are capable of evaporating or coming out of solution.

Drop checkers work very well for our purposes as the main item that affects pH in the drop checker solution is CO2 that is very rapid to go in and out of solution.
 

Hoskins

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Hi All

The computer has now been installed for 2 and a half weeks. First observation / benefit is that prior to installing I was making daily tweeks to my needle valve to keep the CO2 injection in the 'sweet spot' without gasing the fish. Now I input the tank water dkh to the computer and it calculates the ideal ph and keeps it there. I have left the flow from the needle valve set around where it was and therefore the computers solenoid only cuts in around 2-3 times a day. Which proves that too much gas was being used.

During this period I have left the drop checker in place to make sure that I have not made any mistakes which stays constantly green.

I agree that it is an expensive solution but gives me the peace of mind that when I am away not too much gas will be injected and wipe out my livestock.
 
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i'm quite startled after readin the whole of this thread!
A question was asked, the op didnt like the answer got upset an then didnt take on board anything that was said!

The op didnt prove at all that too much co2 was present previous to to ph controller, but more than likely "proved" that using a ph controller "by the book" does not in fact give enough co2!

Yes, the controller tells you a ph value and yes that value changes as you add co2.

It does not however account for other acids that will skew the ph reading. This alone sets the co2 levels wrong!
Also it is a mistake to assume your kh is exactly the value you've read from the test kit.

So, if the 2 variables, ph and kh that are bein used are almost certainly not correct, then how on earth can you use those 2 things to get your 30ppm of co2?

Also i would imagine the op is leavin the controller on all through the night, so a highly possible scenario would be that a short while before lights on, the low limit on the ph controller is reached and co2 is cut off, the lights come on and until the ph has risen to the other "trigger" point, co2 will be low and not bein properly supplied at a crucial time!
 

Hoskins

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I also use a timer as I would without the computer therefore the solenoid is closed 1 hour efore light out and opened 1 hour before lights on.

As a cross check I also use a BC and remains lime green. Therefore the computer keeps the levels in the correct range without the worry that I could overdo especially when I am away or when the CO2 bottle gets low.

Works very well for me and at TGM but everyone has an opinion, which is questionable if you dont have one to test.
 
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i do have one!
which is why i read the post in the first place.
i thought initialy it was the thing to have, nice high techy bit of kit and besides i got it dirt cheap! ;0)

but the more i thought about it, the more i realized that they had big limitations, mine possibly more than yours i believe, the denerrle ph controller turns off at 0.1 below and turns on at 0.1 above the set value, which WILL cause fluctuations in co2 levels that otherwise wouldn't have been present therefore could actually be something that created more problems than it solved.

like the point raised in previous post, that you may have since realized as you currently turn it off at night.
its also something extra that could malfunction when your not there to keep an eye on it!
the probes obviously need regular calibration (another place where errors could occur) plus replacement and they are not cheap.

i'm just putting my opinion across, because it may safe someone a lot of money!!! :0)
if i'd have paid 200 odd quid for this thing i would not have been at all happy when i realized that they serve very little purpose!!
 

Ed Seeley

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baron von bubba said:
i'm just putting my opinion across, because it may safe someone a lot of money!!! :0)
if i'd have paid 200 odd quid for this thing i would not have been at all happy when i realized that they serve very little purpose!!
It's not that they don't serve any purpose, it's just that they monitor and measure something that isn't important (IMHO) in a planted tank. What you want are stable CO2 levels rather than stable pH levels and unfortunately a pH computer fluctuates CO2 levels to gain a stable pH.

If you have a pH computer then simply set it to act as a safety switch that will switch off the CO2 if you get a drop of significantly more than your usual tank conditions.
 

Hoskins

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I agree. As I have been saying all along I basically leave my bubble rate at the original level and therefore the integral solenoid rairly stops the flow but if I make any changes and I am going to be away for a few days I know that when I come back my fish will be safe.

If I did not have the computer the only way to be safe would be to underdose which IMO would be more detrimental to the plants.

However I also agree if I was at home more I could live without the computer and get good results but I dont have time on my hands and this gives me peace of mind.
 

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