W'd there be any thumb rule for co2 injection for a planted tank?
Denerlle company's researchers suggest injecting 50% of the tank's volume as a thumb rule (in a 100 litter tank for example, they suggest injecting 50 bubbles per 1 minute).

What would be any recommendation for 1000 litter tanks and above?

There is no answer to that question, because it all depends on how you inject the CO2 and how much light intensity you have, plus how much plant mass you have and how fast the plants are growing. Plus, of course, how much CO2 you are losing from the water surface. It is infinitely better to just measure the amount of CO2 in the water, using a drop checker, and go by that.

Dennerle should know better than to make that suggestion. They are the only company I know of that understands how the drop checker should be used, and they sell theirs with the reference KH solution and indicator reagent included.

They have "researchers"?

I think I've done more than they have
And I'm just one guy doing it part time.
The rate sounds a bit high, but that's better than too little.
I add about 1 bubble every 3 seconds for a 75 liter very high light tank(which means more CO2 demand).

So that's 20 bubbles a minute for a 75 liter, 100/75 = 1.333 x 20 = 26.67 bubbles per minute for a 100 liter tank.
That's a bit less, but if you diffuser it poorly, that will make a large difference.
I add about 180 bubbles/min on a 135 gal with high light and overflow/wetdry-(510 liters) So that is 100/510 x 180 bubble min= 35 bubbles/min for 100 liters.

Pretty easy to do but makes a lot of assumptions like ADA's bubble counting.

So .......are the bubbles sizes, volume, moles of CO2 all the same?
No.......

Bubble rates are only good for ball park general ranges at best.
A Drop checker or a pH meter with a KH ref is the better option.


Regards,
Tom Barr

Thanks for the comprehensive answers.

Tom, in your experience, what are the best diffusers sold today in the market (from a known company that is sold all over the world) ?

ADA, the Rhinox have done well for me, DIY venturi's and PVC externals etc.

All work well.
Also, see the thread on GDA near the last 10-15 post or so.

Regards,
Tom Barr