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Degassed tank water 24 hrs 8.3, degassed tank water 1 week 8.75.

Co2 on 13:00 pH 8
13:30 - 7.8
14:00 - 7.6
14:30 - 7.5
15:00 - 7.4
15:30 - 7.4
16:00 - 7.4 ( lights on with slow increase to full intensity at 18:00, fluval 2.0 led par around 40 at substrate)
16:30 - 7.4
17:00 - 7.3
17:30 - 7.3
18:00 - 7.3
18:30 - 7.2/7.3 ( wouldn't stabilise a reading )
19:00 - 7.2/7.3
19:30 - 7.2/7.3
20:00 - 7.2
20:30 - 7.2
21:00 - 7.2
21:30 - 7.1/7.2
22:00 - 7.1/7.2 ( co2 off )
Would this be classed as unstable? I'm getting some BBA on leafs edges and substrate. Co2 method is aquario neo acrylic diffuser with a power head above. KH is 9.
 

ian_m

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Seems not a big enough drop. 1 unit pH drop is produced by 30ppm CO2, so you will be looking at a pH of 6.8 at lights on.

You clearly have some CO2 injection and distribution issues.

I assume you are using a pH pen rather than test kit t measure pH ?
 
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Yes I'm using a ph pen, not an expensive one by all means. Ok so I will look into injecting some more to achieve the 6.8 at lights on it will be a fair few bps already on 4. did think it wasn't enough but my drop checker does turn towards more yellow at co2 off when pH is 7.1 although fish seem fine. I have a surface skimmer to allow O2 into the mix.
 
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Good videos Zeus thankyou, I seen his other one about gaseous exchange too. So I've cranked up the co2 and I've lost count of the bps. Currently pH is at 7 although I turnt it up at 4 which pH was 7.3 after co2 started at 13. Just waiting to see how far the pH drops. Tank is like a bottle of Sprite
 

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ian_m

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You also have to remember that the pH scale is logarithmic (bet you wish you had paid attention in school maths lessons now...:cool:).

So a 0.9pH drop is only in the order of 20ppm CO2 and a 1pH drop is 30ppm, thus your 0.5pH drop is only around 15ppm CO2.

See this table to get a rough idea of CO2 levels. This generally under reads CO2 ppm (which is good so as to not gas your fish) as there are other salts and factors in tank water that affect the pH.

co2_graph_zps9c124ef0-gif.gif
 
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Haha yes maths and science! So my kh is 9 which at 7 pH according to the chart I should have 27ppm co2 but as you are saying I would actually have less as it under reads and only accounts for pure water. My degassed tank water after 24hrs reads a pH of around 8.3 but after a week the degassed tank water reads 8.8/8.9. so from a 24hr degassed pH read of 8.3 my target pH with co2 should be 7.3? I went down to 7.04 yesterday and drop checker was yellow. Flow for me seems ok as I see all plants gently swaying but maybe needs another look into
 
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Do i go off degassed tank water after 24hrs at 8.3 to a 1 point drop to 7.3 or use the chart of 9kh and a oh drop to 6.8 and over shoot a little?
 

milesm

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29 May 2019
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HI
forget the chart. it assumes that KH is determined solely by carbonates and therefore underestimates co2 concentration. as for starting pH ideally you would want it fully de-gassed. i've been playing around with not fully de-gassing but still shooting for the pH drop based on fully-degassed level. use less co2 and can achieve the drop quicker.
 

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