Co2 - sufficient produced overnight?

[Martin Fletcher]

Thought this was interesting, in my 'soon to be' Discus tank I've been having a slight problem with low lighting levels until I upgraded the lights to T5 tubes on Tuesday. As it's a planted tank I had Co2 running until the Fire Extinguisher ran out over a week ago.

Yesterday I did a large water change and because I was refilling the FE today I put the Co2 Dropchecker back in the tank with 4dKh water and 2 drops of reagent. Up to lights out last night the dropchecker was, as expected, still showing blue indicating that there's no Co2 to measure in the tank.

However, this morning as the lights came on I noticed the dropchecker was an acceptable shade of green indicating satisfactory Co2 levels - still no Co2 running into the tank from the pressurised system!

I can only assume that as the new lighting has now got my plants photosynthesising properly they are producing the Co2 overnight, as they should of course. The real surprise is that they have produced sufficient to turn the dropchecker green!

Got a real bargain at the FE shop this morning, he refilled my cylinder and then asked why I hadn't got a spare one - good point - he said he could supply a fully refurbished one, guaranteed and full of Co2 all ready to go for £20 and went off into the back to produce one that looked absolutely brand new. He said it was the last one and I could have it for £10 - needless to say I snatched his hand off!

 

[Martin Fletcher]

Thought I'd show the tank so you can see it's not so heavily planted as my community tank. There has been some growth since the photo was taken but it's still not heavily planted.

 

[dw1305]

Hi all,

I can only assume that as the new lighting has now got my plants photosynthesising properly they are producing the Co2 overnight, as they should of course. The real surprise is that they have produced sufficient to turn the dropchecker green!

If you have soft water and a planted tank you will get big pH swings during the diurnal cycle, just caused by the differing levels of CO2 and O2, at night CO2 levels will creep up as all the bioload is respiring and the plants are net producers of CO2, rather than net consumers. The drop checker is just measuring pH.

This sort of pH change doesn't bother the fish etc, but if you want to limit it you can run an air-stone at night or add some dKH.

More in this thread <Drop checker Staying Yellow even with CO2 switched off | UK Aquatic Plant Society>

cheers Darrel

 

[Martin Fletcher]

Ah yes, I had forgotten that it's just measuring the PH which of course changes as it becomes more saturated in Co2 - should have thought of that myself!

Our water is described by the Local Water Board as very hard so it won't swing as much but in my heavily planted community tank where I have the Co2 running a bit higher I do have an airstone on a time-switch for a few hours overnight, just as back up really.

Thanks for straightening me out!

Martin