Hi all,
with four or five inch deep matted cover of water sprite. Some fishes I have not seen in month's .
Know what you mean, I was contemplating thinning the Water Sprite this morning, I think our version of jungle and "heavily planted" are probably a bit different from the average. I'd really like Edvet's triffid (
Ceratopteris pteroides (from <
Restarting 400 gallon | UK Aquatic Plant Society>)) you can imagine it fighting back when you tried to remove it.
Some fishes I have not seen in month's .
When I say to people that I didn't know I had
Corydoras hastatus left, and that I hadn't seen them for months, but when I had to move the tank I found they'd spawned and I had considerably more than I started with, I think they think I'm either lying, deluded or very short sighted.
Is my understanding that in low tech,where only naturally produced CO2 is available,,that plant's use this up within an hour or two after light's on for the day.
The CO2 will definitely be depleted, but there will be more diffusing in all the time, it is going to depend upon tank architecture and water turn-over. If the tank has very low dissolved CO2 levels the concentration gradient between atmospheric and dissolved CO2 is going to be fairly steep, so this is going to act as negative feedback, depleted CO2 = quicker diffusion. I think one reason "Alastair's" and "BigTom's" tanks are so amazing is their large surface area to volume ratios.
If you really wanted to work out what was happening you would need a pH probe and some measure of dKH in the water. You could then measure pH every 15 minutes or so through the photo-period, the rise in pH should give you a pretty good idea of how far the CO2 has been depleted. The rising pH will actually be indicating the degree of oxygen saturation, but CO2 level will be near enough the value given by the dKH/CO2/carbonate relationship.
I've never done it systematically, but when I have dipped the pH meter in before lights on, we've usually been somewhere around pH6.5, and mid afternoon (so well into the photo-period) about pH8. I've also played with the Dissolved Oxygen meter at the same time, and the water is somewhere near 100% saturation.
I would suspect I usually have about 3 - 4 dKH, 100 microS conductivity and pretty low BOD. By mucking about with dKH, the relative changes in pH (much larger as the water approaches 0dKH) should give you a measure of CO2 level. Unfortunately it is difficult to measure dissolved gas levels in water directly.
cheers Darrel