Originally Posted by Tom Barr

About CO2:
I do not pay much heed to keeping the CO2 at a certain set range based on pH/KH readings if things just don't look right in the tank.

If the CO2 measurement is going to be off...................it's going to have less CO2, not more as a general rule. So I'll add a little bit more incrementally. Until I see the plant growth I know I should have and no signs of fish CO2 stress.

The approach is similar to finding optimal Traces levels which are difficult to test for. This gets around poor test kits and focuses on the plants themselves. Some kits are just unable to tell you what you need to know.

Get the rest of the parameters in good ranges, then isolate the variable of
interest.

As long as you have a way of adding a known steady amount(Rate), you can find the CO2 injection amount you need.

Keep adding more till you no long get a good plant response.

I suggested 20-30ppm for plants some time ago by doing this. I'm leeary to suggest others try this without a careful eye, good steady delivery of CO2, turn your CO2 off at night(reduces any errors or build up that might occur with a 24/7 routine).

Years later I found a reference by Bowes on photosynthetic characteristics (CO2 and light saturation maximums) that showned 30ppm as the maximum amount that will help plants.

The "off at night routine for CO2" is similar to the notion I use for dosing of the nutrients(Estimative index).

With the KNO3 etc .....you add a bunch and then do a large water change to remove it all to prevent excess build up.

But with gases, the off gassing at night provides this prevention of build up of excesses. So no water changes are needed to achieve the same result on a daily basis with gases.

Amano does the same thing. Cranks the CO2 in there, then shuts it off at night.

Screw the "pH stability is better" idea. I've never found that to have merit and I've been doing this for over a decade with all these so called wimpy fish.

By isolating the parameter of interest, you get a much better idea of what is going on and how to get around poor testing procedures.

This is what helped me figure many things out were many other folks had problems in the past.

CO2 is a bit tougher due to high levels causing fish issue but still to this day, I've never killed a fish with CO2 gas.

There's also another way to arrive at a close approximation of CO2 with peat.......but that's another post....

Regards,
Tom Barr