ph readings, dropchecker always green and aquasoil... any relationship?

[parotet]

Hi, I set up my new tank 2 days ago. It's a 60 liter tank with 9 liters of Aquasoil Amazonia (around 6 liters of sand), pressurized Co2 and 48w T5 running now only 6 hours. I'm trying now to understand if my CO2 diffusion is correct. To do this, I borrowed a high quality pHmeter from work and I am also using a dropchecker.

The "problem" right now is that my DC is always green (I would say that it turns a bit lime in the middle of the light period, but not really sure). On the other hand what I have done is to note the ph values during these days.

I use Lily pipes and the outflow is quite submerged, doesn't break at all the surface. The ceramic diffuser (2 cm diameter) is in the opposite side of the outflow. I can see the tiny bubbles (0,5 bps/30bpm) nearly reaching the surface and then being transported to the back of the tank. It seems, at least watching the plants and water moving, that the flow is not bad.


tap water pH (I only use tap water): 7.6 and very hard water (don't have test but my area is famous for that)

22h: 6.90
(no readings, just sleeping )
9h: 6.74 (CO2 ON)
10h: 6.67
11h: 6.62 (LIGHTS ON)
12h: 6.60
13h: 6.58
14h: 6.56
15h: 6.51 (CO2 OFF)
16h: 6.59
17h: 6.56 (LIGHT OFF)
18h: 6.55
Then it is suposed to rise to 6.8-6.9. I did this evening a 50% water change with tap water (ph: 7.6) at 19h and the value was after the WC was 6.95, so still far below my tap water values.

I asume that having probably KH values quite high, the pH drop will be of 0.5 maximum, which is more or less the case. Probably I should have these lowest values earlier (by switching on the CO2 earlier?).

On the other hand, it is the first time I use Aquasoil Amazonia and this is the second day, so there might be plenty of things happening in my water column. In the bag you can read that humic acids can be released, especially with alkaline water which is my case...Does it has something to do with my low ph values compared to tap water values?

And coming again to the ever green DC (even before CO2 is on, actually it never goes blue unless I take it outside the tank)... if my water had never reached ph7 during these two days, is it normal that my DC doesn't go to blue? Can you see a clear blue in your DC? When?

Sorry for so many questions and thank you in advance.

Jordi

 

[Andy D]

I am only just a beginner with CO2 so I hope someone else who knows more will be able to help but I think you are right in that the substrate is reducing the pH. I believe it lowers and buffers the pH and is a popular choice for shrimp keepers because of this.

I have very hard water (although I have started to soften it with RO) and my drop checker certainly went back to blue every morning. In fact I was getting a 1 pH drop from co2 on to lights on and my drop checker only ever went a dark green.

Given the starting pH reading I probably would expect more of a drop in pH was needed by lights on. Might need to up the injection rate?

 

[parotet]

Just an hour later of the 50% water change, the pH value is 6.75 (so dropped in one hour 0,2, without CO2 injection)... I will check if the DC goes blue tomorrow morning, but I notice more or less the same trend as yesterday.

 

[Sacha]

My drop checker is always green too.

If you have your Co2 set up in perfect balance, the drop checker should be darkish green in the morning, and light green in the evening.

The Co2 concentration of your tank will not drop too much overnight if the tank had lots of plants, because the plants respire at night, releasing Co2.

If your DC turns blue outside of the tank, you can trust it. If it is always green, don't worry! You are doing everything right.

 

[Spnl]

I have London tap water, pH about 7.6 out of the tap, KH about 12-13 (JBL kit).
My drop checker is always green apart from going lime green to yellow by CO2 off at 6pm.

I think whether the drop checker goes blue or not overnight will depend on how much natural source of CO2 you have and how much surface agitation you have. According to a post on Cichlid forum, the main source of natural CO2 is the filter. Therefore, if you have good flow derived from massive filtration capacity, as many planted tanks have, you would expect lots of CO2 to be added overnight, whereas if your flow is mainly from circulation pumps, you might be gassing off overnight.
As Sacha says, as long the bromothymol blue goes blue when you take the drop checker out, if will be working OK.
Amazonia is supposed to reduce pH, so is a likely cause of your lower starting pH.

The size of pH drop to indicate the desired level do CO2 is a bit more complex. As a scientist, though not a chemist, I find some of the comments on here about how we "should" have a 1.0 drop in pH a bit over simplistic.
PH drops following CO2 addition due to addition of carbonic acid. The amount of pH drop for a given amount of acid added depends hugely on 2 things, buffering (for our purposes mainly KH) and starting pH.
A buffer resists change in pH, so reduces the pH change for a given amount of CO2.
Also, pH is a log scale, so the amount of acid to cause a 1.0 drop from 7 to 6 is 10x as much as needed to cause a 1.0 drop from 8 to 7.
So your pH drop looks quite significant, though the drop checker should go lime green.

A good way to see how much of the pH drop is due to CO2 as opposed to substrate, and how much CO2 is in your water is to take the water sample and leave it out of the tank overnight. I do this regularly, after Ceg suggested it in one of his priceless posts. My tank water is pH 7 ish in the morning, before CO2 on but will rise to 8 if left out all day, but drops to 6.6 by co2 off.
Your pH will drop after water change because tap water contains CO2; my tap water goes from 7.6 to over 8 if left to stand.

 

[Sacha]

Reading pH of the tank water is NOT an accurate way to measure Co2.

I have only been on this forum a couple of days, but have seen loads of people talking about their co2 concentration in terms of a pH drop- how much the Co2 drops their pH.

A drop checker is the most accurate way to measure co2 concentration. pH of tank water is affected by so many other things than Carbonic acid. Humic acids, ammonia (which is acidic), nitric acids, even some algaes, all can influence the pH. Therefore we need to read something which is constant and ONLY influenced by the co2 gas (and the resultant carbonic acid). The way we do that is with a contained amount of water of a known KH, which is not in contact with anything else that may alter its pH.

 

[dw1305]

Hi all,

Reading pH of the tank water is NOT an accurate way to measure Co2....A drop checker is the most accurate way to measure co2 concentration. pH of tank water is affected by so many other things than Carbonic acid. Humic acids, ammonia (which is acidic), nitric acids, even some algaes, all can influence the pH. Therefore we need to read something which is constant and ONLY influenced by the co2 gas (and the resultant carbonic acid). The way we do that is with a contained amount of water of a known KH, which is not in contact with anything else that may alter its pH..

The size of pH drop to indicate the desired level do CO2 is a bit more complex. As a scientist, though not a chemist, I find some of the comments on here about how we "should" have a 1.0 drop in pH a bit over simplistic. PH drops following CO2 addition due to addition of carbonic acid. The amount of pH drop for a given amount of acid added depends hugely on 2 things, buffering (for our purposes mainly KH) and starting pH. A buffer resists change in pH, so reduces the pH change for a given amount of CO2. Also, pH is a log scale, so the amount of acid to cause a 1.0 drop from 7 to 6 is 10x as much as needed to cause a 1.0 drop from 8 to 7. So your pH drop looks quite significant, though the drop checker should go lime green.

This is quite important, if you just aim for a certain level of pH drop you have every chance of asphyxiating your fish. As long as you use 4dKH solution, and a narrow range pH indciator (bromothymol blue), in the drop checker, the carbonate hardness of the tank water should be irrelevant.

Have a look at this post: <Ph drop & high alkalinity | UK Aquatic Plant Society>, it has lost the pH~ CO2~ dKH relationship chart, so I'll post it here.

According to a post on Cichlid forum, the main source of natural CO2 is the filter.

If you have water with a large BOD (Biochemical Oxygen Demand, e.g. raw sewage, landfill leachate etc)) this is true, but I'd be very surprised if that is true for most aquarists, possibly once you get away from hugely over-stocked, non-planted, bare tanks for Mbuna etc. In tanks, which are not entirely reliant on the filter bacteria for biological filtration, I would expect that most of the CO2 comes from the respiration of the non-microbial bio-load (fish, plants etc.).

Therefore, if you have good flow derived from massive filtration capacity, as many planted tanks have, you would expect lots of CO2 to be added overnight, whereas if your flow is mainly from circulation pumps, you might be gassing off overnight.

This wouldn't be true, actually in nearly all biological filtration the volume of the filter media is practically irrelevant, it is the microbial biomass (of both nitrifying and ordinary heterotrophic bacteria) that produces the CO2.

Low BOD means low CO2 production. If you have plants they are removing ammonia before it ever gets to the filter bacteria, the microbial biomass (and BOD) remains quite small.

Flow is relevant, but it doesn't matter whether it is from a power-head or a filter, more flow creates a larger gas exchange surface, and means that dissolved gas levels more closely match atmospheric levels. People who keep non-planted tanks are always teetering on the brink of disaster due to low oxygen/high CO2 levels, but for planted tank keepers the water is fully saturated with dissolved oxygen during the photo period when the plants are actively photosynthesizing.

cheers Darrel

 

[Samjpikey]

I've been using the forum for a while now and the information i have been given is that a drop checker isn't the best method is to measure co2 accurately .... And by purely measuring the ph drop by itself is enough to measure co2 concentration.
So does this mean I am using the wrong method ?


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[Sacha]

Be very wary of those pH/ KH charts, that is working on the assumption that there are NO other acids in the tank!

And there almost always are other acids in the tank which influence pH.

So yes, a drop checker is the way to go. Those charts are a good "rough guide" but definitely not accurate.

 

[Samjpikey]

I've never used the charts just led to believe that a ph drop of 1 by lights on was the rule of thumb .


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[Sacha]

Definitely not.

A pH drop of 1 in a tank with KH 2 and a pH drop of 1 in a tank with KH 10 indicate completely different concentrations of Co2.

As outlined by the chart

 

[Samjpikey]

Yea I understand that by all means . I understand about a difference in kh affects the amounts of co2 needed to saturate the water.
What im saying is that if I have a consistent ph throughout the whole day( this stays at 7.6 even if I inject no co2 for 24 hrs ) when I inject co2 - this drops from co2 on - 7.6-6.6 1 hours later - surely that alone is telling how much co2 is entering the tank by making it more acidic . If no other factors have changed the ph previous to the co2 injection then this has to be true or do the other factors which affect the ph also coincidentally take part at this time ??


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[Sacha]

My point was really that a tank is not a stable and contained environment, there are lots of other things at play other than Co2 and KH.

In a drop checker, there are just three elements. pH, KH, and Co2.

Therefore the drop checker is the most reliable way of measuring Co2. You can do whatever works for you, but there are many other factors in a tank that may affect your pH.

 

[parotet]

Thank you all for the answers... Ok, so as far as I understand:

1. I don't have to be worried if my DC doesn't turn blue.

2. I should try to see a lime green in my DC at least in the middle of the light period

3. DC is the best indicator as it won't be influenced by my substrate releasing right now humid acids (though I must learn to read properly dark green light green and lime green...), but pH meter can help me at least to check if within an hour (between CO2 on and lights on) I have a relevant pH drop which will be very probably due to an increase in the CO2 concentration.

4. The relevance of the pH drop using a pH meter in the water tank depends on the water kH. I think I should try to get at least 1.0 drop and check it with the DC color (which is not influenced as it works with a fix kH) at the end of the photoperiod to see if I would be gazing my fishes or if this drop is not enough.

My pH values and DC colors are the same as yesterday for the moment, even if I began to inject CO2 (0.5 bps) this morning 30 minutes before. I will try first to go to 1 bps and monitor the DC color and pH drop within between CO2 on and lights on.
If this doesn't work, I will try to place the ceramic diffuser under then flow lily pipe, just to check that it is not a problem of flow, but I think that in a 60 cm tank it should not be a problem (outflow in the opposite side of diffuser. I can see the bubbles going backwards and even again to the front of the tank).

Does it sound reasonable?

 

[Sacha]

Yes- absolutely. Good plan.

 

[Samjpikey]

This was mentioned in another thread on this forum .
Hope it helps


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[Victor]

So yes, a drop checker is the way to go. Those charts are a good "rough guide" but definitely not accurate

The chart was made to water inside your drop Checker. Never use your tank water as reference.

 

[Andy D]

3. DC is the best indicator as it won't be influenced by my substrate releasing right now humid acids (though I must learn to read properly dark green light green and lime green...), but pH meter can help me at least to check if within an hour (between CO2 on and lights on) I have a relevant pH drop which will be very probably due to an increase in the CO2 concentration.

So why is the drop checker not affected by other acids? Surely any acid would have an impact on pH?

 

[Samjpikey]

What if your colour blind ??? Sorry just had to


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[OllieNZ]

So why is the drop checker not affected by other acids? Surely any acid would have an impact on pH?

The drop checker is isolated from the tank water by an air gap.