Water Chemistry According To My Seneye

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Offline Helen

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Water chemistry according to my Seneye
« on: October 12, 2017, 10:59:28 PM »
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So I've set up my Seneye again and bought some slides. It is now giving me readings for pH, NH3 and NH4+.

After 24hrs of readings, the NH3 is stable at 0.016ppm. my Seneye is telling me this is good.

My pH seems to have fluctuated between 8.25 and 7.96 (considerably higher than I expected) The noticeable, although gradual dip being at 7am.

The NH4+ graph is essentially the inverse of the pH with a peak at 7am of 19.98ppb (yes, definitely b). From what I was reading last night, and my chemical engineer husband tried to explain to me in sentences I could understand, is that the pH and temperature affect how much of the N molecules are ammonium and how much are toxic ammonia.

In guessing that the reason I've not seen a corresponding change to the NH3, is because it is measured in ppm, not ppb or log.

What could be causing the pH to change?

By the way, the temperature seems to have been stable, fluctuating around 25.5 degrees (+/- 0.2). Also slightly warmer than I'd realised from my analogue thermometer (which I read as just below 25 degrees).

Also, my light controller failed last night, so the LEDs didn't come on till I turned them on about 6:15pm.

Oh and the Seneye is also telling me I have a dissolved oxygen content of 8.1. Which is also apparently ok.

I think my tank is ok?

Offline Andy The Minion

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Re: Water chemistry according to my Seneye
« Reply #1 on: October 13, 2017, 06:44:05 AM »
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@Helen Your husband (or significant engineer) is correct, the Senseye will in all probability be measuring total Ammonia, NH4 plus the toxic NH3, the amount of each is not stable and can fluctuate as a result of both pH and temperature.
Firstly, yes your water is fine. 'Zero ammonia' that is always quoted is not actually possible, it's just 'zero on the test strip/ texture' and you have a system that is more precise.
What supprises me was the low NH4 reading, without checking I was expecting this to be NH3 levels but I'm only a Mechanical engineer so Im probably wrong.
This aside I expect what you are seeing with the fluctuation is the effect of the light cycle on your plants, I'm guessing they come on sometime around 7am and the plants start consuming CO2 in the water which will start to increase the pH. Even if the total ammonia remains constant the toxic NH3? will increase as the pH increases. The plants will also consume Ammonia with the lights on so I was expecting the total reading to decrease slightly but maybe the reduction is too small to see

Offline Sue

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Re: Water chemistry according to my Seneye
« Reply #2 on: October 13, 2017, 09:29:27 AM »
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I agree with Andy. There is always some ammonia in the tank, it is just too low to register on our testers. With Seneye being able to measure tiny amounts, it can see this trace amount.
The 'ammonia' will be NH3 + NH4 together, like with test kits. NH3 in water is in an equilibrium, which I can't type properly as I am missing symbols on my keyboard. (I'll have to use the symbol for reversible equation instead of equilibrium)

NH3 + H+ <-> NH4+

Ammonia and hydrogen ions are constantly joining together and separating, and the amount that are in the NH4+ form at any given instant is temperature and pH dependent. The more acidic the water, the more H+ there is - this is the definition of an acid. With an equilibrium, the more there is on the left side of the equation, the more it is pushed over the right side. So increase H+ on the left (ie making it acidic) and the more it is pushed over to the right, into the less toxic NH4+
In basic water - pH over 7 - the amount of H+ in the left is lower, so the equilibrium is displaced towards the left, so there is more NH3 and less NH4- at higher pH.

I can always complicate things further by saying where the H+ comes from but I'll leave that for now  ;D



pH varies during the day particularly in a planted tank. Plants take up oxygen and make carbon dioxide 24/7 in respiration just like we do. But they also take up CO2 during daylight during photosynthesis and use this CO2 to make carbohydrates. The waste product of photosynthesis is oxygen.
The net effect is CO2 made all the time but CO2 taken up during daylight. There is more CO2 in the water at night than there is during the day. When CO2 dissolves in water it forms carbonic acid. So tank water is more acidic in the dark that it is in the light - the pH is lower at night than during the day. At 7 am the pH should be lowest because all the fish and plants have been 'breathing out' carbon dioxide during the night so there is more of it in the water at the end of the night than at any other time. As soon as it starts to get light the plants start to photosynthesise and remove some of the CO2 so the pH starts to rise.








Offline Helen

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Re: Water chemistry according to my Seneye
« Reply #3 on: October 14, 2017, 12:22:30 AM »
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Thanks @Sue. Really interesting explanation.

Offline Helen

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Re: Water chemistry according to my Seneye
« Reply #4 on: November 16, 2017, 11:03:34 PM »
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So I'm starting to wonder if my Seneye is giving me too much accuracy!  :o

I can see that the pH varies between 7.5 and 7.7 (in a 24hr cycle, more or less). This doesn't sound much, but looks quite dramatic on the graph. 7.5 is generally the top of the pH range for my fish. And knowing that it is a logarithmic scale has me wondering if the high pH could be causing my fish problems.

I realise that if I was testing the pH with a liquid test, I probably wouldn't be able to see the difference of 0.2 and certainly wouldn't know that there is a daily fluctuation.

So am I worrying too much? :yikes:

Offline Sue

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Re: Water chemistry according to my Seneye
« Reply #5 on: November 17, 2017, 08:32:57 AM »
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I have read recently that a change in pH of up to 1 unit won't harm fish so your 0.2 is well within that. This is why it is safe to do water changes where tap water pH is slightly different from tank pH.
I'll have to test the pH of the tank next time I do a water change, and compare it to the tap water I add just to see.

This diurnal change in pH happens in natural water sources as well as our tanks, it is something fish have evolved to cope with. Provided the swing is not greater than 1 pH unit of course.

Offline Helen

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Re: Water chemistry according to my Seneye
« Reply #6 on: January 04, 2018, 12:37:08 AM »
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Recently the pH of my tank has been gradually increasing. And I noticed this evening that it seems to have lost its diurnal cycle. So I wonder whether I just have too many plants using up CO2 and not enough fish to replenish it. It does seem relatively stable over the last week or so, just higher than I'd like. There is a small decrease from 8.11 to 8.03 minimum value where I did 2 X 40l (20%) water changes. I'm wondering whether it is worth doing more water changes to bring the pH down, or if that will just cause more problems by introducing a fluctuation in pH - if the problem is my plants using up all the CO2?

And what would be the best temporary fix until I get more fish? I do have an unused CO2 canister, but it is pretty old so I have no idea how reliable it could be and also whether injecting CO2 on a short term would cause more problems from BBA.

Also if introducing new fish does start to bring down the pH (by balancing co2 production and consumption), does that give me a new limiting rate at which I should introduce fish? I don't want to create a pH crash by introducing too many fish at once and increasing the CO2 as well as the ammonia.

Offline Hampalong

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Re: Water chemistry according to my Seneye
« Reply #7 on: January 04, 2018, 05:29:24 AM »
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You'll only get a pH crash if you run out of KH - or it becomes so negligible that it can't neutralise acids as they're produced.

Sue, it's very wrong to make a blanket statement that a change in pH of 1 unit won't harm fish. What if the pH is at the fish's limit before that change? Or if you've just changed it by 1, and then "a change of 1 won't harm the fish", and then another, etc. You need to know the pH tolerance range of the fish to know whether it can be changed by a whole unit...

I've never been able to see the point of a Seneye, except in a new tank when ammonia is expected (or added). In a mature tank they measure ammonia and pH in amounts/increments that we don't really need to know about.

Offline Sue

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Re: Water chemistry according to my Seneye
« Reply #8 on: January 04, 2018, 09:07:43 AM »
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Re-reading what I wrote, I should have been clearer.
The chap who said that on another forum was assuming a tank of fish kept within their preferred pH range and his comment was that a slow swing during a 24 hour period of up to 1 pH unit should not harm fish, but a swing of over 1 pH unit has the potential to harm fish. The comment was made in reply to someone who has a diurnal pH swing of 0.5 pH.

Offline Hampalong

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Re: Water chemistry according to my Seneye
« Reply #9 on: January 04, 2018, 02:06:42 PM »
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Most freshwater fish experience daily pH changes (and temperature changes) so small relatively slow changes in either are easily tolerated by most. There is even evidence to suggest that both daily and seasonal temperature changes, at least, are beneficial to fish. A lot of the temperature ranges given for fish actually seem to be 'summer' breeding temperatures and that we're actually stressing our fish by keeping them at a constant temperature (which is far too warm).

Offline Helen

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Re: Water chemistry according to my Seneye
« Reply #10 on: January 18, 2018, 10:16:05 PM »
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Look what has happened to my pH profile since I added the fiveband barbs. It has gone almost flat. The variation now seems to be +/- 0.04. I will be testing the GH and particularly the Kh at the weekend (when I am at home in daylight. Just realised that I don't need daylight for those tests as they are colour change. Will do them tomorrow!)

Edited to add that the down blip is when I added the new fishing the tank. I tried sticking my Seneye in the bag to monitor the ammonia build up while the temperature was balancing. The green block at the bottom, with the lines on it indicate that is where I added a comment to the log (to say that new fish are being added)

Offline Matt

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Re: Water chemistry according to my Seneye
« Reply #11 on: January 19, 2018, 05:31:54 AM »
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That is interesting...  not only has it dropped, but also stabalised as well.  how much did you increase your stocking by when you added the fivebands? Have any of the other variables changed? 

I know you have a theory about co2 levels in the tank... which does make sense but id expect more variability in a planted tank as he plants use co2 only during the day. I'm also wondering if there being more ammonia produced (but not necessarily being allowed to build up in your planted tank) could have the same effect... or if the plants growing faster as a result of more co2/nutrients would lower pH... @Sue ?

Offline Helen

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Re: Water chemistry according to my Seneye
« Reply #12 on: January 19, 2018, 07:01:24 AM »
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I'm going to have to do more tests to find out what is going on.

I completely agree about the variability.   :o

The other thing that has changed slightly is the ammonia. It has slightly reduced since last water change, from 0.032, to 0.028 and again to 0.026 since the fish were added. The scale of the graph for ammonia is terrible, so this trend can't actually be seen graphically (it is measured in increments of 0.02).

So I wondered if there has been enough of an increase in co2 for the plants to start growing and using up other nutrients, but not enough to show an increase in CO2?

The stabilisation is a surprise to me, and I currently have no real ideas what's caused it!

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Re: Water chemistry according to my Seneye
« Reply #13 on: January 19, 2018, 07:10:43 AM »
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The stabilisation is good news, even if you can't work out the cause.  :cheers:

Do the plants look as if they've had a bit of a growth spurt?

Offline Helen

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Re: Water chemistry according to my Seneye
« Reply #14 on: January 19, 2018, 07:48:41 AM »
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The plants in my tank have deliberately been chosen as slow growing, so 3 days isn't enough to be able to see a growth spurt!

It is good that the pH has stabilises. I'd just prefer it to stabilise slightly below the pH of my tap water rather than slightly above!  :o

And my tank is supposed to be slightly acidic.  :vcross:

Online Littlefish

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Re: Water chemistry according to my Seneye
« Reply #15 on: January 19, 2018, 07:58:51 AM »
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 ???
I have no explanation for you, I'm afraid.
The more involved (obsessed) I get with aquatics, the more I realise that I don't know enough.  :-[

Offline Sue

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Re: Water chemistry according to my Seneye
« Reply #16 on: January 19, 2018, 09:12:37 AM »
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I'll try and get my head round this (not sleeping well at the moment due to very poorly mother) but I may end up being a bit vague.
More fish = more CO2 and more ammonia. CO2 makes the water more acidic, ammonia makes it more basic. Plants also make CO2 24 hours a day and take up CO2 during the day but not in the dark. Net result - less CO2 in the water during the day compared to at night, therefore less acidifying chemical during the day compared to at night.
I will confess that I have no idea whether plants take up ammonia 24 hours a day but logic says they must or we'd wake up to fish suffering the effects of ammonia every morning. In heavily planted tanks there are not enough bacteria to remove all the ammonia during the night if the plants do switch off.


But none of this explains the results. More fish = more CO2 so you would expect a bigger day/night swing; unless the plants have settled and started growing at the same time you got the barbs.
There are countless micro-organisms live in the substrate and a lot of these break down fish poo etc releasing CO2 as a result - one reason a tank with a good amount of fish and slow growing plants does not need added CO2. You have been messing about with the substrate - are we seeing the result of the micro-organisms re-establishing themselves and producing CO2 at a rate which is keeping the level, and thus pH, more stable?
And with this scenario we have more fish and more micro-organisms making more CO2 24 hours a day so the pH will be slightly lower.


More fish = more ammonia. Plants and bacteria take it up as fast as the fish make it. The amount present in the water after it leaves the fish but before it reaches a plant/bacterium is very tiny; far too small for ordinary testers.
Is this slight drop due the plants recovering from the shock of the rescape, and more bacteria establishing themselves?


I am too tired to think this through to its logical conclusion, so I've thrown out some ideas to see if other members can connect them  :)

Offline Helen

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Re: Water chemistry according to my Seneye
« Reply #17 on: January 19, 2018, 10:06:39 AM »
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Hope things improve with your mother @Sue

Your suggestions certainty make sense. I'll  investigate further and let you know the results.

Offline Helen

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Re: Water chemistry according to my Seneye
« Reply #18 on: January 22, 2018, 12:49:05 AM »
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So I did another, slightly less comprehensive set of water tests today.

GH 5 drops (90ppm)
KH 2-3 drops (54-72ppm?) I'm try to write this by memory as I've left my results downstairs!
Phosphate has gone up to slightly above 1ppm (but still less than the next reading which is 2.5)
And nitrate is 5ppm. I also realised that the nitrate reading I gave last time was incorrect. I was puzzling over my reading, when it dawned on me that I'd been reading the colour chart incorrectly. I think it was also 5ppm - knowing the result I got last time and what I was doing wrong.

And my pH has started to come down. It looks like it has reduced a total of 0.25 over a week and a bit of a daily variation has started to reappear. See attachment for the last week's readings.

So what I wondered is whether the new fish increased the amount of CO2 fairly quickly, but it took a few days for the amount of nitrogen to increase. And because the nitrogen was so low, this had been the rate limiting factor and therefore the plants hadn't really been using the CO2. Hence the stable pH throughout the day. But as the fish increased the amount of nitrogen in the water, the plants started to grow again and the CO2 cycle started to reappear.

Anyway, I will keep monitoring things.

The other thing I realised that I'd done last week, was turn off my secondary pump. It is only small to ensure adequate water circulation behind my huge, solid piece of bogwood. But with the lower substrate, and more water volume above the wood, it didn't seem to be hampering the water flow as much as it used to. But I realised that the pump has been improving the flow across my Seneye and that could affect the readings. Anyway, I've turned it back on this evening, so I'll see what happens to the readings over the next 24hrs (or so).

As there are more fish in the tank, I have been feeding more this week than I have for a while. (Also watching the new fish!) And I'm pretty sure that the increase in phosphate is a sign I have been overfeeding the fish. So they got a smaller portion this evening and I think they'll probably have a fast day tomorrow. Depending on my Seneye readings tomorrow night.

Of course, @Sue 's theory on plants and substrate inhabitants recovering and settling could be right. But I guess I won't know until the next time I add more fish. Which could be next weekend seeing as it's my birthday on Saturday!  :cheers:

(My husband bought our daughter a usb microscope for Christmas. It has a 1000x zoom. Oh the things we have seen in our house since :sick: :yikes: And of course, the fish tank is perfect for finding microbeasts. But only if they are within about 5cm of the front of the glass. So I've had a glimpse of the sort of things my kuhlis hunt for!)

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