Poor Growth

I should say - there are no algae that the pleco would eat,
because I am fighting a battle with long hair algae. I am picking it and
manage to keep it in control, but it is annoying.

That's a sign that something is out of balance in your tank. I've heard some
people say that hair algae is a sign of too much iron; you may be
overfertilzing. All of your plants are relatively slow growers, and your light
level is moderate, so you may not need too much fertilizer.

You might also consider adding some water sprite or Hygrophila. You can even
just let it float at the top of the tank. Fasting growing plants help a lot in
keeping algae under control.

On the CO2 - I am curious to understand why that system is not adequate.

The system you have wasn't really designed for a tank the size of yours. The
Hagen thing is basically just DIY CO2, with yeast and sugar. It works well for
small tanks, but is often inadequate for large ones.

Some people make yeast and sugar CO2 systems work for large tanks, but it takes
some work. They often buy special wine yeasts (that last longer), use larger
containers for the fermentation, and run two or three batches at once.

It is giving out several
bubbles a minute and they dissolve before the reach the surface in the
"trap" that came with the system.
How would I figure out how many bubbles are needed?

It's impossible to say, because each tank is different. That's why you use a
CO2 chart, to see how much CO2 is actually getting into the water.

However, here are some factors that affect the amount of CO2 you'll get:

Surface turbulence -- Surface agitation dissipates CO2. For that reason,
people who inject CO2 often modified their filters and place their powerheads
and spray bars so they don't disturb the surface of the water.

Size of batch -- You may be able to get your CO2 levels up by using larger
batches of yeast and sugar, or running two at once. (Stagger them so that one
is starting up as the other is peaking.)

Amount of lighting and plants -- The more light and the more plants you have,
the more CO2 you need.

Reactor or diffuser -- Basically, the device that dissolves the CO2 into the
water. I don't know how effective the Hagen reactor is, but many people have
reported that injecting the CO2 directly into the filter is the best way to
dissolve CO2 into water.

Tank cover -- A tight cover will help keep the CO2 in.

If you don't want to upgrade your CO2 system, you probably don't have to.
While more CO2 would be desirable, you seem to have enough. The Hagen system
is probably doing you some good, even if it doesn't create Amano-like CO2
levels.


Leigh

http://www.fortunecity.com/lavender/halloween/881/