Turned lights on to a yellow drop checker

[Robsvespa]

Evening all ... I woke up this morning to a yellow drop checker. The tank is quite heavily planted and it's been running for about 3 weeks at a co2 rate of 2 bubbles per second, the drop checker reading green before I go to bed and green when I turn the light on the next day ... until this morning.
I'm aware that plants stop photosynthesising in the dark and kick out co2 instead but is this enough to turn my checker yellow overnight ? Or are my plants not consuming co2 efficiently enough in the day (and all of a sudden ?)
It's a 40 gallon tank with 54watt t5 light, with a mix of low light and medium light plants which are all growing fine.
I use fertilisers weekly and dose a co2 booster daily.
If any of you kind people could help me out I'd be most appreciative ... Thank you.

 

[Julian]

Have you made any adjustments to your surface agitation? If you've lowered it then the amount of CO2 in your water will increase.

 

[Soilwork]

Also I think drop checkers are a few hours behind and are an approximation. The checker may have still been entering the yellow stage well after lights off. The colour change back may be slower at night too.

I had my co2 on for 8 hours today and the checker only turned lime in the last hour and a half.

 

[Robsvespa]

Thank you both for your quick response ... The water agitation is the same as it always was, breaking the surface gently.

 

[Robsvespa]

My checker never usually changes from its green state, I don't even let it get to lime green so I don't think its a natural occurrence as it's randomly happened one time over night.
Embarrassingly I think I may have solved the problem on my own. I keep Axolotls in my planted tank and they're fed dead unfrozen fish, this results in a filmy white residue building up on top of the water column inside the drop checker, as it's made up of fish oils and the odd scale it's essentially decaying matter producing and releasing co2 directly into the ball chamber.
I usually clear it out with my finger and it's good for a couple of days but just realised I haven't done it since Sunday, the white residue has got quite thick so I'm guessing that explains the sudden random co2 change ?
Would you agree with that ?

 

[Soilwork]

I wouldn't be able to comment on that. I have only been using my drop checker for a few days. I noticed whilst using mine today that their seemed to be a large bubble spanning the entry orifice if my checker. I don't know if this is normal or not. Just hope it wasn't blocking gas from entering.

hopefully that will turn out to be the problem for you.

 

[Robsvespa]

That large bubble is just where your water ends and the trapped air inside your checker starts, is completely normal.

 

[Soilwork]

Thanks

 

[HiNtZ]

Has your tank temperature dropped at all?

I find when around 25c I need 6bps (I run a sealed sump) for 5 hours before lights on to get a lime green dc.

I've since dropped the temp to 23c because I've had problems with my hc and now I am at 3-4bps for 3 hours before lights on for a lime green dc.

 

[HiNtZ]

Forgot to say that the bubble you mention is perfectly normal. Whether water rides up inside the dc a bit, or if you have a bubble almost lapping over the edges.... It's fine and will not affect it' function.

The dc doesn't rely on gas actually entering it (in fact, having co2/o2 bubbles going in can throw you think you have desired co2 saturation, and you won't - hello algae bloom! ) The atmosphere in the channel will always equalize to the gas content of the water through the membrane.

 

[Robsvespa]

I don't have a thermostat in my aquarium on account that I keep Axolotls and they're coldwater.
6 bps seems a lot, do you keep fish or any livestock ?
I've since ditched my drop checker as I'm pretty certain it's giving me unreliable results. Always on day 3 after a water change my dc turns yellow and no matter what I do it doesn't turn back. I put this down to the White film that forms ontop of the bubble in the dc cos my Axolotls are fine and showing no signs of stress even with a yellow drop checker present for a whole week.
I'm currently running my co2 at 1 bps, I have 1 pink 54w HO tube light overhead.
I'm now using just observation of my animals to ensure I don't add too much co2 .... too early to say if this ammount of co2 is benefitting my plants.