Restocking A Slightly Acidic, Softer Water Planted Tank

I'm going to copy the above comment in my post about my Seneye. Then that post can be a comprehensive review of using a Seneye.

Hmmm, whilst this does count technically as a 'single point calibration'...

The slide may be manufactured to a high degree of precision so that it displays accurately the right colour for the right pH which the probe in the Seneye is looking for. But the probe itself may drift with time. Like our eyes get worse with age, the probe will start to read differently over time.

That said this will normally only happen over a very long period of time (not a week!).

The proper way to calibrate a probe is to use solutions of a known e.g. pH and see what the probe reads and adjust it at two points so take a reading with a solution at pH4 and at pH9 for example and ensure the probe reads 4 exactly and 9 exactly so all values inbetween should also read accurately.

Anyway... for the level of accuracy were after in the hobby Seneyes approach is fine... So you can ignore my rant!!

But I'll carry on anyway... 

We are interested in changes in pH more than the exact pH value.  For example  Seneye will tell you that your pH is changing rapidly as an indicator of something going wrong in the tank. It will also tell you if your fish are compatible by telling you the "reasonably precise" pH level.  If a fish is compatible with a pH range from 6.5 to 8.  And the Seneye says it's 7.3 you know you are good to go. If it says 7.9 you are a risk.  The fish will not suddenly die at 8.1 but it's life may be shortened, however this will aslo be the case at 7.9 just not by as much. As an opposing example, water companies test pH with dual calibrated instruments because they have to deliver water between two defined values. So in the above example if the pH was recorded at 8.1 they could be fined by their regulators... as such they want to be sure it's 8.1 exactly and not 7.99999 meaning they are within their limits.

I feel like I've got my rant out now 

Sorry @Matt for laughing at your rant. 

So my last water change was on the 5th November. The peak pH seems to be between 7pm and 10pm and on the 6th was 7.56. This evening the pH was 7.80. So an increase in 0.24 over 17 days. (I'm not entirely sure if I would have picked this up with a liquid test)

I know that I am still "deep cleaning" my tank, so could it be a hangover of neglect?

The other thing that changed at last water change was the addition of more plants. And some algae growth.

Just thinking about it, I think the Seneye does have the ability for multi point calibration. On the page where I can 'trim' the values, it appears to have a sliding scale. Actually, looking at it again, it isn't multi point. The sliding scale is just the GUIs way of displaying the 'trim'.

Out of interest, the 3 things that can be trimmed are temp, pH and NH3.

Could it be the balance of CO2? In that the plants and fish don't produce as much CO2 as the plants use up in the light? Therefore the plants gradually use up the CO2 that was in the tap water. Because I have so many plants, I do have the filter outlet set for minimum surface agitation. Or would all the CO2 off gas in a 24hr period?

I feel some tap water tests coming on...

Thanks @Littlefish . Could you link that conversation for me, please?

My tank pH isn't changing much. 0.24 is one colour band on most liquid test kits.

I think its this one
https://forums.thinkfish.co.uk/general-fishkeeping-advice/changing-ph-in-tanks/

The pH seems to almost directly follows the lighting pattern. The first peak is about lunchtime, just before the lights go out for the siesta. And the tank is in the lounge, so the evening peak is higher because we usually have the lounge lights on (additional background lighting)

The only thing I can think of is that my tank is no more than 20% stocked with fish at the moment. And that the consumption of CO2 during lit hours exceeds it's generation during lights off.

If that is the case, the trend should change as I increase my stock.

So I'd like to start buying new fish this weekend. 

But I'm a bit worried about the pH of my tank. It is supposed to be neutral to slightly acidic (and all the fish I have chosen are suitable for this), but it is currently 8.1 - 8.2.

I plan to do all the water tests that I have tomorrow (Nitrate, P, K, GH, KH, 6 in 1 test strip that includes pH, nitrate and both hardness).

I suspect that the high pH is due to lack of CO2 (and Kh buffering), because the pH variation with lighting has more or less disappeared. But how do I check this? I have a CO2 kit, but I've not used it for at least a couple years, so I'm not sure how to check it works (properly) and am slightly worried about causing a pH crash if my Kh turns out to be low (which I suspect, but can confirm tomorrow).

I will post test results, and then ask for suggestions, I guess.

It could be the snail shells but I would still test the rocks. It is worth knowing everything there is to know about tank decor 

Do I test the rocks by dripping kitchen vinegar on them? Or some other way?