Thanks Tom. I really appreciate your comments and I'm gonna go in that direction. One more question though. Is using the ph controller the best way to automate c02? The way I have it programmed right now is to keep ph between 6.75 and 6.8 and shut off completely at night. I guess I should lower it to ~6.15 with a kh less than 1. What do you think?

Steve

Rather than concerning yourself with pH, why not try to maintain a steady ppm of CO2 during the days? And, trying to make that ppm be about 30 ppm? You can use a drop checker, with 4 dKH distilled or deionized water in it, to do that. Then, if you make sure there is good water flow throughout the tank, such that leaves on all of the plants are swaying in the flow, you can probably eliminate CO2 as being a problem. The fish will continue to do well with the soft water, and if you don't go much above 30 ppm of CO2, they will do well with the CO2.

Well, the key word here is automation. I'm routinely out of town a couple weeks at a time. I've spent a lot of effort on my dosing and water change systems and they are now fully automated. I know that kh and ph are directly related to c02 levels and of course you can't go strictly by the chart, with so many other things affecting ph, but there should not be a problem establishing a base line standard in my tank, like you said using a drop checker, and using the ph controller to keep the c02 levels constant without having to check them.
Does that sound reasonable?

In 2 weeks, the level of growth in my tanks would throw off the CO2, nutrients and would be nothing more than a moving target.

You need an automated pruning device to go along with all the rest.
Auto dosing is not going to give the results you think.

How does growth affect things?
Water flow?
CO2, lighting, nutrient demand(does 2-3x more biomass, 3x more light as it grows to the surface use less, or more CO2 and nutrients?).


You cannot automate somethings.
You only have a few things and few trade offs.

Given these constraints, non CO2 might be wiser.

Regards,
Tom Barr

I've used Potassium carbonate, Sodium bicarbonate and Potassium bicarbonate.

It's very hard to get Potassium bicarbonate in less than 20Kg bags! Plus of course it has a side-effect of altering the pH of the water.
It dissolves very fast and raises KH and pH.

Potassium carbonate only raises KH. Though it takes longer to dissolve in the water. I live in Scotland where the water is ~0 GH and ~1 KH...

Aqua Essentials sells Potassium carbonate. If you know of a USA seller, I'd be interested as I need a USA supplier for the following page:

Potassium carbonate - The Aquarium Wiki

I'd prefer to use Potassium carbonate, then Potassium bicarbonate then Sodium bicarbonate. But the last item is the easiest to get and cheapest.

If you want to add K and only raise KH, get Potassium carbonate.

Oh, that sounds like something I would really be interested in having. Can I set it to top and replant, or does it only do pruning? My early experiments with automated pruning devices only ended in disaster: the silicone-sealed Roomba, augmented with scissors and suction cup wheels, left a wake of destruction in my tank and soon became wedged behind some driftwood and ended up gnawing its way through my filter intake pipe right before it shorted out and electrocuted my fish. I'm glad someone has finally gotten it figured out

Larger scissors makes the job easier if you are a "topper" pruner.
I've been more a uprooting pruner most of my life and topping was an easy out.
Some plants respond well to topping, some do not.

Some like most things , a trade off ensues.........a mix of both methods seems best.
Still,. if you need KH, KHCO3 works nicely.

Regards,
Tom Barr